Base on the physical model of multilayer insulation(MLI) outside the satellite,the temperature model of MLI was established,considering the radiation heat transfer,solid thermal conduction and residual gas conduction.The infrared radiation of MLI included self-radiation and space environment radiation.At last,combined with the given orbit,the temperature field and infrared radiation was obtained.The calculation result showed the most energy of infrared radiation was concentrated on far infrared radiation band,and the energy of reflecting the earth infrared radiation accounted for 45% nearly.