In order to make the missile owner achieve the purpose of penetration, the mathematical model of the surface temperature of space targets is applied to calculate the temperature field distribution of targets at different heights on the basis of analyzing the background radiation. And the influence of height on infrared radiation characteristics is analyzed and discussed. The results show that the height is not the parameter which can distinguish the decoy and the warhead by day or by night, but deployment in the day time can reduce the hit rate and achieve the penetration effect.