The invention discloses caching data synchronous system and method in a process of accessing an iSCSI (Internet Small Computer System Interface) storage device. The system and the method can judge whether caching data volume of a virtual disk is qualified or not after receiving a data access request sent by a starter to the virtual disk appointed by a target terminal and starting a caching data synchronizing process of the virtual disk; if qualified, the data access of the virtual disk is blocked and the data access of the virtual disk is opened after an appointed operation is carried out, and an access request is restarted to normally respond; and if not qualified, the access request of a starter end is responded by selecting a normal response or sending a busy response mode according tothe current state of a counter or the counter. Therefore, the system and the method can complete the caching data synchronization and can keep that the data access of the started end is not stopped.