In the existing RPKI system, the open source tool Rsync is used to synchronize data between the RPKI databases and the RP servers. However, due to the particularity of the certificate data structure in the RPKI system, data synchronization using Rsync not only is inefficient, but also consumes too much system resources, so that the entire RPKI system suffers potential security risks. Therefore, the IETF proposes an incremental synchronization Delta protocol to replace Rsync's role in RPKI. This paper introduces the working logic and mechanism of Delta protocol in detail, compares it with Rsync in terms of security and efficiency, constructs the Delta protocol model by using Promela language, and verifies the model with formal verification tool SPIN. It proves that the protocol has high protocol security and stability. Finally, this paper presents the Delta protocol implementation structure, in order to offer reference and communication.