I finally found out the solution from AgileBits:
After updating to the new iCloud CloudKit engine in OS X Yosemite and iOS 8, you may see two 1Password sync files in your iCloud storage. One is from the old engine and the other from t he new engine.
As it is difficult to tell the two apart, the easiest method is to reset sync for 1Password entirely. Since both the Mac and iOS device have local copies of the data, we can remove and regenerate iCloud data easily.
We’ll do most of the work on the Mac.
- Disable iCloud sync on all devices.
- iOS: In 1Password, tap Settings > Sync > Sync Service > Disable iCloud.
- Mac: Open 1Password and click 1Password > Preferences > Sync > Change Syncing > Disable Sync.
- Remove the newer iCloud data.
- Click Help > Troubleshooting > Erase iCloud data.
- Remove older iCloud data.
- Open System Preferences and click iCloud. Click Manage. Click the remaining 1Password entry, then click Delete All.
- Restart all devices.
- Set up iCloud again.
- Mac: Open 1Password and click 1Password > Preferences > Sync > iCloud.
- iOS: In 1Password, tap Settings > Sync > Start Syncing > iCloud.