According to the characteristics of optical fiber self-cure ring networks， a synthesis synchronization method for line differential protections is proposed. The method uses the results of ping-pong method as the primary criterion and results of reference phasor method as the auxiliary criterion. The method proposed can implement self-adaptively data synchronization with the auxiliary criterion to distinguish the working state of self-cure ring network. When the reference phasor method is used to synchronize data， the distance blocking logic is added to improve the reliability of protection. Testing results of real-time data simulator（RTDS） show that the method is easy to operate and has reliable performance.