Abstract: To address the performance degradation of permanent magnet synchronous motors (PMSM) under complex operating conditions caused by parameter variations, load disturbances, and model uncertainties, an improved super-twisting sliding mode control method based on cascaded extended state observer (CESO) is proposed. A cascaded linear and nonlinear ESO is constructed to achieve rapid estimation and effective compensation of the total disturbance, thereby enhancing the disturbance observation accuracy and suppression capability of the system. Meanwhile, an improved super-twisting sliding mode control law is designed to strengthen system robustness and reduce control chattering. Finally, simulation studies are carried out in the MATLAB/Simulink environment. The results show that, compared with conventional control methods, the proposed method exhibits superior performance in speed tracking, disturbance rejection, and steady-state accuracy, demonstrating its effectiveness and feasibility.