Lateral support has a significant effect on the deformation of thin primary mirror. This paper deals with the analysis and optimization procedure on the “push-pull-shear” lateral support of thin meniscus mirror. Three steps were carried out in the lateral support optimization. Firstly a finite element model (FEM) was build for further analysis, then according to its structural characteristic, the ratio between the tangential force and the radial force was analyzed during the first optimization; In order to make the lateral forces with the same value, equal angle distance was changed to different angle distances during the second optimization, also lateral support position and magnitude of the lateral forces were given; during the last analysis, a portion of axial force was exerted at the inner ring, the response curve between the inner ring axial force and the RMS in Z direction of the mirror was plotted. The final result showed that the RMS value was decreased from 12.168nm to 3.253nm in Z direction. The optimization procedure provided a feasible way for lateral support of thin meniscus mirror.