diff --git a/src/main/java/com/mosquito/project/service/ActivityService.java b/src/main/java/com/mosquito/project/service/ActivityService.java
index b7a7539..bfa85ff 100644
--- a/src/main/java/com/mosquito/project/service/ActivityService.java
+++ b/src/main/java/com/mosquito/project/service/ActivityService.java
@@ -12,6 +12,9 @@ import com.mosquito.project.exception.FileUploadException;
 import com.mosquito.project.exception.InvalidActivityDataException;
 import com.mosquito.project.exception.UserNotAuthorizedForActivityException;
 import org.springframework.cache.annotation.Cacheable;
+import com.mosquito.project.persistence.entity.ActivityEntity;
+import com.mosquito.project.persistence.repository.ActivityRepository;
+import java.time.ZoneOffset;
 import org.springframework.stereotype.Service;
 import org.springframework.web.multipart.MultipartFile;
 
@@ -43,54 +46,81 @@ public class ActivityService {
     private final AtomicLong apiKeyIdCounter = new AtomicLong();
 
     private final DelayProvider delayProvider;
+    private final ActivityRepository activityRepository;
 
-    public ActivityService(DelayProvider delayProvider) {
+    public ActivityService(DelayProvider delayProvider, ActivityRepository activityRepository) {
         this.delayProvider = delayProvider;
+        this.activityRepository = activityRepository;
     }
 
     public Activity createActivity(CreateActivityRequest request) {
         if (request.getEndTime().isBefore(request.getStartTime())) {
             throw new InvalidActivityDataException("活动结束时间不能早于开始时间。");
         }
+        ActivityEntity entity = new ActivityEntity();
+        entity.setName(request.getName());
+        entity.setStartTimeUtc(request.getStartTime().withZoneSameInstant(ZoneOffset.UTC).toOffsetDateTime());
+        entity.setEndTimeUtc(request.getEndTime().withZoneSameInstant(ZoneOffset.UTC).toOffsetDateTime());
+        entity.setRewardCalculationMode("delta");
+        entity.setStatus("draft");
+        entity.setCreatedAt(java.time.OffsetDateTime.now(ZoneOffset.UTC));
+        entity.setUpdatedAt(java.time.OffsetDateTime.now(ZoneOffset.UTC));
+        entity = activityRepository.save(entity);
+
         Activity activity = new Activity();
-        long newId = activityIdCounter.incrementAndGet();
-        activity.setId(newId);
+        activity.setId(entity.getId());
         activity.setName(request.getName());
         activity.setStartTime(request.getStartTime());
         activity.setEndTime(request.getEndTime());
-
-        activities.put(newId, activity);
+        activities.put(activity.getId(), activity);
         return activity;
     }
 
     public Activity updateActivity(Long id, UpdateActivityRequest request) {
-        Activity activity = activities.get(id);
-        if (activity == null) {
-            throw new ActivityNotFoundException("活动不存在。");
-        }
+        ActivityEntity entity = activityRepository.findById(id)
+            .orElseThrow(() -> new ActivityNotFoundException("活动不存在。"));
 
         if (request.getEndTime().isBefore(request.getStartTime())) {
             throw new InvalidActivityDataException("活动结束时间不能早于开始时间。");
         }
 
+        entity.setName(request.getName());
+        entity.setStartTimeUtc(request.getStartTime().withZoneSameInstant(ZoneOffset.UTC).toOffsetDateTime());
+        entity.setEndTimeUtc(request.getEndTime().withZoneSameInstant(ZoneOffset.UTC).toOffsetDateTime());
+        entity.setUpdatedAt(java.time.OffsetDateTime.now(ZoneOffset.UTC));
+        activityRepository.save(entity);
+
+        Activity activity = new Activity();
+        activity.setId(entity.getId());
         activity.setName(request.getName());
         activity.setStartTime(request.getStartTime());
         activity.setEndTime(request.getEndTime());
-
         activities.put(id, activity);
         return activity;
     }
 
     public Activity getActivityById(Long id) {
-        Activity activity = activities.get(id);
-        if (activity == null) {
-            throw new ActivityNotFoundException("活动不存在。");
-        }
+        ActivityEntity entity = activityRepository.findById(id)
+            .orElseThrow(() -> new ActivityNotFoundException("活动不存在。"));
+        Activity activity = new Activity();
+        activity.setId(entity.getId());
+        activity.setName(entity.getName());
+        activity.setStartTime(entity.getStartTimeUtc().atZoneSameInstant(ZoneOffset.UTC));
+        activity.setEndTime(entity.getEndTimeUtc().atZoneSameInstant(ZoneOffset.UTC));
         return activity;
     }
 
     public List<Activity> getAllActivities() {
-        return new ArrayList<>(activities.values());
+        List<Activity> result = new ArrayList<>();
+        for (ActivityEntity e : activityRepository.findAll()) {
+            Activity a = new Activity();
+            a.setId(e.getId());
+            a.setName(e.getName());
+            a.setStartTime(e.getStartTimeUtc().atZoneSameInstant(ZoneOffset.UTC));
+            a.setEndTime(e.getEndTimeUtc().atZoneSameInstant(ZoneOffset.UTC));
+            result.add(a);
+        }
+        return result;
     }
 
     public String generateApiKey(CreateApiKeyRequest request) {
@@ -214,7 +244,7 @@ public class ActivityService {
 
     @Cacheable(value = "leaderboards", key = "#activityId")
     public List<LeaderboardEntry> getLeaderboard(Long activityId) {
-        if (!activities.containsKey(activityId)) {
+        if (!activityRepository.existsById(activityId)) {
             throw new ActivityNotFoundException("活动不存在。");
         }
         // Simulate fetching and ranking data
@@ -232,7 +262,7 @@ public class ActivityService {
     }
 
     public ActivityStatsResponse getActivityStats(Long activityId) {
-        if (!activities.containsKey(activityId)) {
+        if (!activityRepository.existsById(activityId)) {
             throw new ActivityNotFoundException("活动不存在。");
         }
 
@@ -246,7 +276,7 @@ public class ActivityService {
     }
 
     public ActivityGraphResponse getActivityGraph(Long activityId) {
-        if (!activities.containsKey(activityId)) {
+        if (!activityRepository.existsById(activityId)) {
             throw new ActivityNotFoundException("活动不存在。");
         }