The rapid development of the network technology, especially that of the fieldbus, is changing the traditional control system. In order to solve the problem of the linkage synchronization and the network data transmission of the Multi-Ac Servo system, we recently designed a CAN bus protocol named CANServo. It is a high-level protocol of CAN bus , it is used to replace traditional parallel data transmission between NC and servos. In this study, we described the method to solve the synchronization problem, the setting up of the communications, the strategy of dynamic reorganization of priorities, the structure of the buffer track and the operation of the track. In the end, we illustrated the results of the experiment which the correctness of our design can be proved by.