Abstract: Copper powder (Cu) pigment was modified with silane coupling agent (KH550) as modifying agent.The effect and mechanism of Cu pigment modified with different coupling agent concent rations on mechanical property，infrared emissivity and corrosion resistance property of 50% Cu/polyurethane (PU) composite coatings were investigated in detail. The results indicate that the Cu pigment is modified by silane coupling agent successfully. Compared to that of Cu pigment without modification，low inf rared emissivity 50% Cu/PU composite coatings treated with a suitable coupling agent concent ration still keep the low value of 0.1 in 8～14μm. However，the adhesion of the coatings is improved from grade 2 to grade 1；the hardness is increased f rom 4H to 6H. The anti-alkaline，anti-acid and anti-salt times are improved from 1h to 90h，50h to 60h，10h to 50h before the emissivity of the coatings is increased，respectively. The modification of Cu improves the interfacial compliance between Cu and PU，and results in higher compactness of the coating.