This paper describes an object oriented modeling technique of an interior permanent magnet synchronous motor (IPMSM) drives for a dynamic simulation of a hybrid vehicle propulsion system. In order to enhance reusability of the model, each part of an IPMSM drive system is modeled in an object-oriented manner according to the physical partitioning of the drive system. This model allows comprehensive analysis of the IPMSM drive, including torque fluctuation of IPMSM, switching strategies of an inverter, and complex algorithm of a controller and it is also possible to simulate in a simplified way for a reduced computation time without considering switching patterns of an inverter. This model is implemented in Simulink environment, which is a de facto standard tool in control and system engineering, and is easily integrated with other models of hybrid propulsion system. By use of the developed model, fundamental characteristics of IPMSM drive system were investigated and the simulation results show its practical effectiveness.