This paper simulates a thermal environment in a passenger cabin with CFD. In the simulation, the SIMPLE algorithm and k-ε turbulence model are used, the natural convection is taken into consideration and the body-fitted coordinate is applied. This paper also investigates the effect of component radiation in the cabin. The results indicate that for most regions where the air velocity is low, component radiation plays an important role and can not be ignored. The results also show that the configuration of vents has a significant influence not only on the velocity and temperature levels but also on the overall flow topology.