Abstract: The elastic finite-deformation problems be bring into the theoretical system of Lagrangian mechanics, the basic equations of finite-deformation for plane-strain problems and plane-stress problems be builded by the Routh method in classical mechanics,the contradiction in von Kármán equation of finite-deformation large-deflection problems be disussed, and thenew plan be proposed in this paper.

Key words: Lagrange formalism, Routh's method, Finite-Deformation problems