Abstract: To explore the main self-structure factors affecting the thermal distortion of rigid antenna reflector in orbit, a spaceborne honeycomb sandwich structure model with a diameter of 1.2 m was analyzed. Firstly, by altering the skin material, the thickness of adhesive, the property include stiffness and coefficient of thermal expansion (CTE) of honeycomb, a finite element simulation software was used to calculate the root mean square (RMS) of the thermal deformation of the reflector when the ambient temperature changes from 20℃ to -80℃. Furthermore, the causes of each factor were analyzed. Secondly, two typical honeycomb sandwich structure reflectors of M55J and T300 skin materials were prepared by autoclave molding process so as to validate simulation results. The results indicate that the thermal deformation of the M55J skin material reflector is smaller than that of the T300. In addition, there is a linear relationship between the thermal distortion and the thickness of the adhesive, the thinner the later, the smaller the former. When the thickness of the adhesive layer is constant, the thermal deformation of the honeycomb is the dominant factor. The effect of the skin stiffness on the thermal deformation of honeycomb is obvious as the increasment of the stiffness value is 2 times. Moreover, when the normal CTE of honeycomb is changed by 11 times, the relative increment of thermal deformation is more than 80%. The thermal distortions of the two typical reflectors were measured as the environment temperature changed from 20℃ to -80℃. The difference of the thermal distortion between simulation and testing is 15.7% and 15.2%, respectively, which proves the simulation results are reliable. By optimizing the corresponding parameters can provide reference for the design of spaceborne antenna reflector.