Abstract: Thermal and optical performance of the radiometric calibration optical structural system under space simulation conditions can affect the precision of the radiometric calibration test for satellite IR remote sensor. In this paper, a finite element model of radiometric calibration optical structural system is built, which consists of an off-axis paraboloid mirror and a secondary mirror. It is convenient to use the orthogonal Zernike annular polynomials as the data transmission tool. Firstly, the least squares method is used for the polynomial fitting. Secondly, the Zernike coefficients are input into the ZEMAX software and the imaging quality of the optical system under space simulation conditions is analyzed. The results show that the thermal gradient of the optical structural system has an important effect on the rigid displacement of the optical bracket, but not so much on the off-axis paraboloid shape. The imaging quality error is about λ/37. By comparing with the results of accurate in-situ measurements of imaging quality parameters by Foucault tester, the results of the thermal structural optical integrated analysis in this paper are validated.