In view of the weakness of robustness in the process of synchronization of non-uniform air-gap permanent magnet synchronous motor (PMSM) chaotic system, which is easily affected by parameter perturbation and external disturbance, based on the dynamic model of PMSM drive and response synchronization error, a finite time chaotic synchronization control method based on sliding mode observer is proposed. The sliding mode observer is used to realize the on-line observation of the uncertain load. Combining the sliding mode theory and the finite time stability theory, the approximate decoupling of the nonlinear and linear terms of the system is realized by active control, the finite time stability control is used to enhance the robustness and fast response of the system, and the finite time synchronization control method is designed, and simulation verification is carried out under the condition of parameter perturbation and external disturbance. Results show that the proposed control method has faster dynamic response and robustness, and is more suitable for synchronization control of PMSM chaotic systems in complex environments.