The flow field over hypersonic small blunt bodies at zero incidence were numerically simulated by VSL equations with the nonequilibrium chemical source terms. The boundary condition of the wall temperature was improved. The discrete coordinate method to solve radiation transfer equation under body fitted coordinate system was established. And the 7 species air shock layer radiation field of small blunt head body in reentry was simulated by this method combined with band model. The influence of absorption coefficient error on the computational result of head body radiation field was investigated in the ultraviolet region(0.2～0.4μm), visible region(0.4～0.8μm)and infrared region(0.8～2.0μm).