In order to improve the current decoupling effect of permanent magnet synchronous motor (PMSM), an active disturbance rejection control (ADRC) method with current decoupling based on PI observer (PIO) is proposed. In this method, PIO and extended state observer are combined to estimate the disturbance accurately in real time, and the observed disturbance is fed back to the input as compensation value, so as to realize the current decoupling between d and q axes and suppress the disturbance. The disturbance tracking performance of the improved ADRC and the disturbance rejection performance and stability of the closed-loop control system are analyzed theoretically. The results of simulation and experiment show that the disturbance estimation ability of ADRC is enhanced and the decoupling effect of current loop is improved after introducing PIO, which verifies the feasibility and effectiveness of the proposed method.