[Objective] In field-oriented control (FOC) system of traditional permanent magnet synchronous motor (PMSM), the speed loop and the stator dq-axis current loops typically adopt proportional integral (PI) control, which results in a significant speed overshoot. Although sliding mode control (SMC) can reduce overshoot, it still suffers from slow dynamic response and significant current ripple. [Methods] To address these issues, this study adopted super-twisting sliding mode control (STSMC) to regulate the speed outer loop and stator dq-axis current inner loop to improve response speed and suppress speed and current ripples, thereby enhancing the dynamic and steady-state performance of the system. Furthermore, to improve system robustness under external load disturbances, an extended state observer (ESO) was designed to observe disturbances. By treating the load as an extended state variable, the proposed method reduced speed recovery time and mitigated speed drop during sudden load torque changes through feedforward compensation, thereby enhancing system robustness. [Results] Simulation results showed that under an operating condition of 1 000 r/min reference speed and 10 N·m step load, compared with speed SMC, the STSMC reduced the speed regulation time by 86.25%, the root mean square error (RMSE) of speed ripple by 95.35%, the d-axis current ripple RMSE by 45.44%, and the q-axis current ripple RMSE by 34.31%. Compared with speed SMC, the STSMC based on ESO (STSMC-ESO) reduced the speed regulation time by 86.25%, the speed ripple RMSE by 95.70%, the d-axis current ripple RMSE by 45.61%, and the q-axis current ripple RMSE by 37.02%. Moreover, under external load disturbances, compared with STSMC, STSMC-ESO reduced the speed drop by 21.81% and the speed recovery time by 90%. [Conclusion] The STSMC-ESO strategy effectively reduces speed overshoot and enhances dynamic response speed. Meanwhile, it suppresses system chattering and significantly reduces speed and current ripples, thus improving steady-state performance of the system. Under external load disturbances, the system can quickly recover speed and maintain relative stability.