According to bench test results of fuel economy and engine emission for the real power-train system of EQ7200HEV car, a 3-D performance map oriented quasi-linear model is developed for the configuration of the powertrain components such as internal combustion engine, traction electric motor, transmission, main retarder and energy storage unit. A genetic algorithm based on optimization procedure is proposed and applied for parametric optimization of the key components by consideration of requirements of some driving cycles. Through comparison of numerical results obtained by the genetic algorithm with those by traditional optimization methods, it is shown that the present approach is quite effective and efficient in emission reduction and fuel economy for the design of the hybrid electric car powertrain. According to bench test results of fuel economy and engine emission for the real power-train system of EQ7200HEV car, a 3-D performance map oriented quasi-linear model is developed for the configuration of the powertrain components such as internal combustion engine, traction electric motor, transmission, main retarder and energy storage unit. A comparison of numerical results obtained by the genetic algorithm with those by traditional optimization methods, it is shown that the present approach is quite effective and efficient in emission reduction and fuel economy for the design of the hybrid electric car powertrain.