Abstract: In order to accurately calculate the influence of rotor eccentricity on the motor, the dynamic eccentricity caused by load during the manufacturing, assembly and use of a permanent magnet synchronous motor (PMSM) is investigated. A bidirectional magnetothermal coupling analysis method was proposed, which considered the influence of temperature change on motor material properties and fed back to electromagnetic analysis for multiple iterative calculations. Taking 120-slot 48-grade PMSM as the research object, a bidirectional magnetothermal coupling model of PMSM was established and the model was simulated based on rated working conditions. The effects of rotor dynamic eccentricity on the loss, temperature rise, electromagnetic properties and radial unbalance magnetic pull of PMSM were solved and analyzed. With the increase in rotor eccentricity, the magnetic density of the air gap is unevenly distributed and radial unbalanced electromagnetic force is generated. Among them, the radial electromagnetic density harmonics play a major role in the low-order and odd-order harmonics, resulting in the increase of PMSM loss and temperature rise. The comparison shows that the magnetothermal bidirectional coupling is closer to the real data and has higher analysis accuracy and reliability.