Abstract: The IR spectrum from CO2 in hypersonic flow fields along stagnation line was studied; the influence on total IR radiation from hypersonic target by CO2 was analyzed. Using CFD method, the physical conditions of near-space hypersonic flow fields along stagnation line were calculated for sphere target. According to the flow fields' calculation, the spectrum of CO2 in hypersonic flow fields in different flying conditions was calculated using Line-By-Line method. And the radiation from CO2 was also estimated for ablating condition. According to the theoretical calculation, the IR radiation from CO2 in hypersonic flow fields along stagnation line without ablation is far less than the IR radiations from solid craft self, but in ablating condition, CO2 in shock can not be ignored.