Aiming at the problem of high precision synchronous control of the joints of manipulators, a fractional order reaching law which was different from the traditional reaching law was selected. A cross coupling control structure was proposed. A synchronous control strategy of fractional order reaching law based on the variance virtual principal axis was proposed. The stability of the proposed control strategy was proved. Simulation was carried out for a two joint manipulator. The simulation results showed that the proposed control strategy could make the tracking error and synchronization error of the manipulator system converge quickly, and had faster response speed and stronger robustness.