Collgen-g-PMMA copolymer and indium oxide nanoparticles were prepared by grafting copolymerization of methyl methacrylate onto collagen and sol-gel process separately, and collagen-g-PMMA/indium oxide nanocomposite was prepared by ultrasonic wave irradiation. Simultaneously two collagen/indium oxide nanocomposites were prepared by liquid-liquid dispersion and ultrasonic wave irradiation respectively in the interest of infrared emissivity investigation (8-14Am). Three nanocomposites were characterized by SEM, TEM, IR spectroscopy, thermogravimetric analysis and infrared emissometer. SEM and TEM indicated that three nanocomposites were of different microstructures, and that collagen-g-PMMA copolymer and indium oxide nanoparticles self-assembled into homogeneously spherical aggregates of 600nm in diameter, which is owing to, we proposed, the high activity of amphiphilic collagen-g-PMMA copolymer nanoparticles. It was found that two nanocomposites showed significantly lower infrared emissivity value than their components, but the rest one did not. Decrease mechanism of infrared emissivity value of nanocomposite was discussed based on microstructure. It was assumed that the decrease in infrared emissivity value of collagen-g-PMMA/indium oxide nanocomposite was attributed to strong interfacial interactions between collagen-g-PMMA and indium oxide.