A torque closed-loop flux-weakening (FW) control strategy of interior permanent magnet synchronous motor (IPMSM) based on search coils (SCs) is proposed in this article. The proposed strategy adopts a three-closed-loop control structure, where the torque closed-loop is constructed to improve the torque control accuracy, then the voltage vector angle is controlled by the torque regulator to maximize the dc-link voltage utilization, and finally, the current control model is constructed from a novel view and enables the dq-axis current to be controlled by the qd-axis voltage regulator. Subsequently, an improved torque estimation method is proposed, which utilizes the motor magnetic field information collected by SCs for torque estimation. The estimation accuracy of the method is not affected by the motor parameters and operating state because the flux linkage of the motor can be directly observed. Ultimately, the combination of torque, voltage, and current loops enables the motor to operate adaptively at the optimal operating point without the need for motor parameters, as well as maintains accurate torque output and improves the efficiency and torque output capability of the motor. Finally, the feasibility of the proposed method is verified by experiments.