In vacuum deposition, the substrate deformation caused by sustentation and temperature grads can affect the final surface form of film-substrate system. By finite element analysis and calculation on initial stress of different substrates under different sustentation manner, and the thermal stress caused by the interior temperature grads of substrate, P-V values of the substrate surface deformation are gained, and the contours of substrate deformation in different situations are plotted. This analysis shows that the deformation induced by gravity and the thermal deformation are great when its size is over 200 mm, which become the important factor affecting the final film surface form; with the augmentation of substrate obliquity when fixed, the substrate deformation and the stress show decreasing trend; in the same situation, the deformation induced by gravity of the fused silica substrate is a little greater than that of the BK7 glass substrate, while the thermal deformation quantity of the former is further less than the latter; the thermal stress has made greater contribution on substrate′s initial stress.