Abstract: During the service of space-borne antennas in orbit, the extreme thermal variations in space environment significantly affect their surface accuracy, and even interfere with the working attitude of the antenna and its accessories, causing the spacecraft to fail. This paper uses ANSYS finite element software to establish the finite element thermal-structural analysis numerical model of a three-layer 19-module deployable antenna structure. Considering the non-uniform temperature field of space in an extreme thermal alternating environment, the failure mechanism and characteristic response of thermal deformation of the antenna structure during on-orbit operation are analyzed. The research shows that the antenna structure is affected by the jump of solar radiation heat flow when entering and leaving the shadow area, and the temperature gradient develops rapidly. After fully entering the shadow zone, the transient temperature drop of the structure increases, and the thermal deformation increases obviously with the decrease of temperature, and reaches the peak at the edge of the outermost module. By selecting a reasonable constraint position, increasing the thickness of the metal reflector, the cable's diameter and the chord's size, the structure's thermal deformation can be significantly reduced. In contrast, the sizes of the center rod and the vertical rod have little effect on the thermal deformation of the antenna structure. The structural optimization method and thermal control protection measures of space deployable antennas are proposed, providing a reference for optimizing antenna structures and on-orbit service performance.