The open-circuit fault of semiconductor power switch is a common fault in permanent magnet synchronous motor (PMSM) drive system. If this fault is not detected in time, it will cause abnormal operation of the system, bring economic losses, and even endanger personal safety. Recently, the model predictive current control (MPCC) method is widely used in PMSM drive system due to its simple structure and excellent dynamic performance. However, there are few research works that focus on the open-circuit fault diagnosis of semiconductor power switch in PMSM drive system with MPCC method. The previous fault diagnosis methods are mainly aimed at PMSM drive system with conventional control method. Therefore, this paper proposes a diagnosis method of semiconductor power switch open-circuit fault to improve the reliability of PMSM drive system with MPCC method. The cost function is used to detect the abnormality of PMSM drive system. And the stator current and the drive signal of the semiconductor power switch are used to complete the fault diagnosis. The proposed fault diagnosis method is robust against the operating point and parameter mismatch of PMSM drive system. The simulation results verify the effectiveness of the proposed fault diagnosis method.