Based on the criterion of 4K radiation temperature difference, this paper inferred and calculated thermal camouflage condition of infrared pattern paint for the 8～14μm waveband thermal camouflage , including the emissivity difference range of upper surface of target and backgroundΔεts , and the emissivity difference range of spots adjacent to each other on top surface of targetΔεt12. The paper also discussed the factors influencingΔεts andΔεt12.