To overcome the trade-off between high performance and system chattering in conventional Sliding Mode Control(SMC), and to improve the reliability and pointing accuracy of an aeronautical photoelectric stablization platform based on Permanent Magnet Synchronous Motors(PMSM), an approach law for sliding mode controller was proposed. The law can effectively weaken the chattering of the system and achieve a better tracking effect. On this basis, to increase the bandwidth of the disturbance observer and the accuracy of the observation, an Extended State Observer(ESO) was introduced into the servo system of the photoelectric stabilization platform to observe the total disturbance of the system.Further, the lumped disturbance was compensated within the sliding mode controller to better suppress the chattering of the system and improve the system′s ability to resist external disturbances. Experimental results demonstrate that the sliding mode controller, combined with ESO, performs better than the traditional PI+DOB control method. In the uniform speed tracking experiment, the RMS value of the system′s position pointing error is observed to be merely 0.005 7°, which completely satisfies the requirements of the aeronautical photoelectric stabilization platform, and the accuracy is observed to be approximately three times as high as that of the classical PI+DOB control method. In the sinusoidal wave tracking experiment, the proposed method is observed to greatly reduce the phase lag of speed tracking, and the position pointing error is detected to be merely one-sixth of that of the PI+DOB method. In the trianguler wave tracking experiment, the RMS of the position pointing error is approximately one third of that of PI+DOB method.