Abstract: ［Objective］ The circulation water pump adopts a shielded three-phase AC asynchronous pole-changing motor. During the high-speed to low-speed mode transition and the low-speed to high-speed mode transition, this motor requires an extended power interruption period, resulting in significant drops in both motor speed and process loop flow rate. To address this mode transition challenge, a novel bidirectional control strategy for seamless switching between high-speed and low-speed operation modes is proposed at the paper. ［Methods］ First, taking the pole-changing motor of the circulation water pump as the analysis object, a simulation model of the pole-changing motor was established based on the pole-changing principle and the mathematical equations of AC asynchronous motors. A simulation model for low-speed and high-speed drive control of the pole-changing motor was then constructed. To minimize the flow rate drop during the switching process, with the goal of reducing motor speed drop, the dynamic characteristics of parameters such as the motor's residual electromotive force and speed during mutual switching between high-speed and low-speed modes were investigated. Concurrently, considering the operational constraints during pole-changing motor mode transition, a control strategy for switching from low-speed to high-speed and from high-speed to low-speed was designed. The proposed control strategy was applied to the development of the frequency converter power supply for the circulation water pump. Bench tests demonstrated excellent compatibility between the power supply and the circulation water pump. ［Results］ The experimental results confirmed that smooth switching between high-speed and low-speed operation modes were achieved, and operation mode switching requirements for circulation water pump. During the transition from high-speed to low-speed mode, the speed fluctuation was controlled within 22.7% and the flow fluctuation was maintained within 22.7%. Conversely, during the transition from low-speed to high-speed mode, the speed fluctuation was limited to 25.4% and the flow fluctuation was kept within 25.5%. ［Conclusion］ The pole-changing strategy proposed in this paper for switching between high-speed and low-speed operation modes of circulating water pump motors effectively resolves the challenges of operational mode transition, demonstrating significant engineering applicability.