Abstract: For onboard satellites, the satellite antenna is subjected to the periodic temperature change, along with the thermal deformation on the antenna reflector, and the loss of the antenna gain. The coefficient of the thermal expansion, as an important parameter to describe the thermal deformation of the structure, varies with the temperature. If the coefficient of the thermal expansion is taken as a constant in the simulation analysis of the thermal deformation, there would be non-ignorable error. In this paper, for the reflector of a parabolic antenna, with consideration of the variations of the thermal expansion coefficient against the temperature, the influences of the thickness of the reflector, the position of the support, and the selection of material on the thermal deformation of the reflector made of ULE glass and M55 laminate are simulated and analyzed. It is shown that for a parabolic antenna, the error of the reflector is the largest when the support constraint is in the center position. The optimization scheme with the ULE glass can reduce the surface error by about one order of magnitude. In the practical design, the mass, the stiffness, and the modal characteristics should be considered carefully.