6-band P-1 radiation model is introduced to implement the simulation of three-dimensional air arc plasma. The calculation has the specific feature that both radiation emission and self-absorption are taken into account. The distributions of temperature and radiation flux density are obtained and analyzed. Comparing with the net emission coefficient (NEC) method，its temperature distribution range is wider and the arc column voltage is more close to the experimental test value，which shows that the P-1 model can be used to solve the arc radiation problem more accurately.