[Objective] To address the issue of large cogging torque, low motor efficiency and high torque ripple commonly found in canned permanent magnet synchronous motor (CPMSM), this paper aims to analyze the influence of asymmetric permanent magnet structure on the performance of CPMSM. [Methods] Based on the arc-shaped permanent magnet commonly used in engineering, this paper adopted the geometric centerline of a single permanent magnet as the reference. The unilateral eccentric design of the permanent magnet was realized by offsetting the centers of its inner and outer diameters, and three asymmetric permanent magnet structures were proposed. The key motor performances of CPMSM with different permanent magnet structures, including air-gap flux density, induced electromotive force, unilateral magnetic pull of the can sleeve, demagnetization coefficient of permanent magnets, motor losses and operating efficiency, were systematically compared and analyzed under no-load and load conditions. [Results] The results showed that the three asymmetric permanent magnet structures shared basically the same performance variation trend. As the offset of the permanent magnet center increased, the amplitude of air-gap flux density decreased. The amplitudes of cogging torque and can loss decreased accordingly, and the motor efficiency was improved. Without taking manufacturing difficulty and cost into account, the left-side asymmetric structure was the optimal scheme. The motor with this structure obtained the highest efficiency and power factor, the smallest drop in output torque, and the most prominent suppression effect on torque ripple. In addition, the unbalanced magnetic pull caused by the asymmetric permanent magnet exerted a negligible effect on the overall performance of the motor. Compared with the conventional optimization scheme of stator-tooth slotting, the proposed method suppressed cogging torque while maintaining favorable electromagnetic performance, and exhibited remarkable advantages. [Conclusion] The asymmetric permanent magnet structure proposed in this paper achieve remarkable performance in weakening cogging torque, suppressing torque ripple and improving the comprehensive performance of CPMSM. Although this structure brings a certain degree of magnetic-circuit unbalance, it does not alter the overall magnetic-circuit distribution characteristics of the motor, and the motor still maintain excellent electromagnetic performance. This study provides references for the optimal design of CPMSM.