In the present study, numerical simulation coupling convection and radiation in vehicle was done to analyze the formation of the temperature field under the non-uniform thermal condition. The scaled cabin model of simplified compact car was used and the thermal condition was determined. The fore floor, the top side of the inst. panel, the front window and the ceiling were heat source. The lateral side walls were cooled by the outdoor air and the other surfaces were adiabatic. It is same with the experimental condition presented in Part 5. In order to analyze the individual influence of each heat source, Contribution Ratio of Indoor climate (CRI) index was used. CRI is defined as the ratio of the temperature rise at a point from one individual heat source to the temperature rise under the perfect mixing conditions for the same heat source. The simulation results showed the large gradient of the air temperature in the vicinity of the ceiling above the front seat and the temperature in other area was almost 18°C. There was circulating flow inside the cabin from the supplied jet to back flow to fore along with the floor. The comparison with the measurement result showed the tendency of that higher temperature had the larger difference between the simulation and the measurement. CRI distribution gave the contribution of the individual heat source to the temperature field and the front window affected to the wide area temperature in the vertical center section of second opening compared with the other heat source.