Aiming at the cracks of supporting structure of deep mixing wall, the elastoplastic behavior of internal force and deformation of deep mixing wall is analyzed in this paper. According to Mindlin plate theory, the thick plate model and three dimensional finite element model of wall are set up. Considering vertical and horizontal bending moment and tortile moment action together, equivalent bending moment is proposed in this paper to evaluate anti-bend capability of wall. Using the program developed by authors, spatial shape of horizontal displacements and equivalent bending moments of wall of supporting structure of deep mixing wall are gained. The calculation results indicate that the cracks of wall are mainly caused by strut´s loads of Huanqiu Plaza beside east of wall.