Among all kinds of motor drive systems, permanent magnet synchronous motor (PMSM) with its high energy density, high efficiency, fast response and other advantages is widely used in electric drive systems in the applications of electric vehicles. However, the distribution of non-sinusoidal magnetic field, the cogging effect and inverter causes torque ripple to produce the large amount of electromagnetic noise in the electric drive system. A variety of optimization and improvement measures are put forward by scholars. In this article, the research results at home and abroad in recent years are summarized, including the cogging torque ripple with skewing-slot method and fractional slot method, current harmonic torque ripple with iterative learning control, repetitive control method, closed-loop torque control method and harmonic current injection method. The advantages and disadvantages of various methods are analyzed and summarized, which provides a theoretical guide for improving the comfort of electric vehicle and the reliability of electric drive system.