In order to reduce antenna reflector weight, the aluminum alloy is replaced by resin composite. The 3D model of antenna reflector was designed. The model of antenna reflector with two kinds of material were simulated by finite element software. The results show that the composite antenna reflector fundamental frequency is 35.23% higher than that of aluminum alloy at the same volume and the weight reduces 41.2%. The thermal deformation of antenna reflector with two kinds of material were simulated at the temperature between -180℃ and +80℃, the composite reflector thermal deformation is 94.25% less than aluminum alloy while the plies are[0/45/-45/90]_2s to the composite reflector root mean square (RMS) is 0.027 mm, the RMS stabilization of composite reflector is superior to aluminum alloy in deep space.