Abstract: For various applications, the develoment of optical window is a multi-discipline engineering effort, which involves optics, mechanics and thermology.Under the circumstance of pressure difference, as well as axial and radial temperature difference, the finite element model (FEM) of optical window is established. The FEM was compared with the theoretical results and validated. Taking FEA data as the input at the interface of modified Zernike polynomial structural/optical analysis, the Zernike coefficients corresponding to aberrations are abtained. Using the obtained Zernike coefficients as the figure of optical window, wave aberration and MTF as measure of imaging quality, the impact of optical windows deformation on optical performance of largeaperture and long focus collimator was analyzed.The results show that the impact is negligible.