The invention discloses a CAN communication protocol of a finished automobile bus control system. The finished automobile bus control system comprises a finished automobile control unit, CAN nodes and a CAN bus which connects the finished automobile control system with the CAN nodes, CAN communication frames for transmitting commands in the CAN communication protocol of the finished automobile bus control system are 29 bit extended frames, and a multi-customer model is adopted in the CAN communication protocol. According to the CAN communication protocol of the finished automobile bus control system, the supporting number of the CAN nodes is increased by increasing the length of the communication frames, a communication model is optimized by the adoption of the multi-customer model, real-time communication is well supported, the communication protocol supports object dictionary reading and writing, the configuration design is optimized by optimizing the NMT management mode, and then support of finished automobile fault diagnosis is achieved.