Aiming at the problem of large amount of calculation in the process of multi-step model predictive current control of surface mounted permanent magnet synchronous motor (PMSM), a multi-step model predictive control with optimal calculation of cost function is proposed. The optimization calculation of cost function adopts the event trigger mechanism, and the calculation amount of multi-step prediction is dynamically reduced by setting the threshold of cost function. Simulation results show that the multi-step model predictive current control performance of cost function optimization calculation is good, which is completely equivalent to the traditional method, also the control effect is equivalent. Based on STM32H743 single chip microcomputer platform, the optimization method and traditional method single control cycle execution time. Experimental results show that for multi-step prediction, the optimization algorithm can reduce the single control cycle execution time, two-step prediction to 77.71%, three-step prediction to 53.95%, four-step prediction to 39.76% and five-step prediction to 33.48%. It is shown that the control performance is the same as traditional calculation method, but the real-time performance is improved.