Uninterrupted operation during open-circuit faults (OCFs) without the assistance of additional circuits or hardware poses a challenge to the fault-tolerant capability of conventional three-phase permanent magnet synchronous motors (PMSMs). Although it is theoretically inevitable for a three-phase motor to experience torque ripple during OCFs, employing fault-tolerant control methods can alleviate this problem. According to the optimal current control principle, a fault-tolerant control method is proposed to address the issue arising from a single open-switch fault in this paper. To ensure continuous operation and minimize torque loss ratio, optimal reference currents are deduced using the maximum torque criterion and Fast Fourier Transform. Meanwhile, a smooth transition method of optimal currents is designed to decrease the torque drop duration. Consequently, the feasibility of the developed fault-tolerant control approach is validated through both simulated and experimental tests.