There are both permanent magnet torque and reluctance torque in permanent magnet-assisted synchronous reluctance motor (PMaSRM). The proportion of different torque components and torque ripple are important indexs to evaluate the rationality of electromagnetic structure design of motor. Taking a 3 kW PMaSRM as the research object, considering the influence of magnetic circuit saturation and d/q-axis cross coupling factors, the torque separation and torque ripple separation of the motor is carried out by the frozen permeability method. Based on the separation result of torque components and torque ripple components, with the goal of reducing the cogging torque under load, the optimization design of motor rotor structure is carried out, which provides reference value for the design of PMaSRM.