[Objective] In the field of modern industrial automation, the dynamic performance of the speed loop of permanent magnet synchronous motors directly affects the operational efficiency and stability of the system. Currently, factors such as load torque disturbances and parameter variations have a significant impact on the dynamic performance of the speed loop, limiting the application of the motor in high-precision and high-dynamic response scenarios. [Methods] To address this problem, this paper proposed a variable parameter proportional integral (PI) control strategy based on the adaptive sliding mode load torque observer. This strategy innovatively combined the high-precision estimation capability of the sliding mode observer with the adaptive characteristics of variable parameter PI control. By capturing the transient changes in load torque in real-time through the sliding mode observer, the PI controller was driven to dynamically adjust the proportional and integral parameters, enabling the system to maintain optimal control under different operating conditions and achieve global dynamic optimization. [Results] The effectiveness of the proposed control strategy was verified through simulation and experiment. The results showed that the variable parameter PI control improved the dynamic response speed by approximately 27.5% compared with the traditional fixed-parameter PI control. Compared with the normal PI dual closed-loop control, the system overshoot was reduced by 20.6%, the recovery time was reduced by 56.6%, and the response time was reduced by 50% through the speed loop variable parameter PI control with load torque identification compensation. [Conclusion] The proposed control strategy effectively enhances the dynamic response speed, steady-state accuracy and anti-disturbance capability of the speed loop of permanent magnet synchronous motor, significantly enhances the system control effect, and shows good engineering application prospects in the fields of new energy vehicles and industrial robots.