Engine torque fluctuation is a great threat to vehicle comfort and durability. Former researches tried to solve this problem by introducing active damping system, which means the motor which is directly coupled to engine shift is controlled to produce torque ripple with just the opposite phase to that of the engine. By this means, the torque fluctuation produced by the motor and the engine can be reduced. In this paper, the author attempts to propose a special used motor for HEV (Hybrid Electrical Vehicles), by changing the traditional structure of the motor which can produce ripple torque by itself. Therefore, four kinds of motors have been investigated and compared. Among which, SRM (Switched Reluctance Motor) has larger torque ripple, which means higher possibility to match with engine’s torque fluctuation while PMSM (permanent magnet synchronous motor) has relatively high efficiency and is widely used, which means lower fuel consumption for the whole system. Hence, these two kinds of motors are simulated. And results show that simply reducing the number of magnetic poles is hard to match the engine’s torque ripple due to its higher frequency of fluctuation. But we can’t deny the possibility of other ways and more investigations and researches need to be done.