Abstract: Zernike polynomials are used as interface for opto-mechanical analysis because the items of Zernike polynomials have corresponding meanings to Seidel aberrations, because the result of finite element analysis can not be directly used by optical software. At present, optical-axis component of nodal surface displacement to the original surface is fitted by Zernike polynomials, which is not accurate. Some algorithms of surface corrected displacement are described and compared. Each corrected displacement is compared with specific examples, and they are fitted by Zernike polynomials. From the difference of fitting coefficient, it is discovered that the corrected displacement must be adopted if the surface curvature is large. It is concluded that both axial and normal corrected displacements adopt the method from original nodes if the original surface equation is unknown, the axial corrected displacement uses the method from the deformed nodes and the normal corrected displacement makes use of the methods from original nodes if the original surface equation is known.