A heating system and a reasonable structure of the air duct structure are designed, to achieve the purpose of improving the passenger compartment thermal environment. The structural parameters of the heating system are optimized. Aiming at the four factors such as the chamfer radius of the air outlet, the angle between duct axis and X axis, the height of the outlet and the type of return air grille on the thermal environment of passenger compartment, according to the orthogonal test theory, the optimal design scheme is determined, and the optimal design scheme is that the chamfer radius of the air outlet is 60mm, the angle between duct axis and X axis is 110°, the height of the outlet is 570mm, the type of return air grille is Z-6-280×5. The CFD simulation of the optimal design is carried out, the temperature of heads and feet of driver, passenger 1 and passenger 2 are monitored, the result show that the heating system of the optimal design can greatly improve the thermal sensation of driver, passenger 1 and passenger 2.