For a primary mirror with the diameter 2 060 mm in large aperture based-ground telescope, parameters of new arch light-weighted structure are detailedly designed with the material SiC. Meanwhile, radius of supporting rings is also optimized. According to 18-point and 27-point Whiffle tree support scheme, mirror deformation for two models is analyzed and contrasted individually in statics (gravity effect) and thermodynamics. Considering the processing technic of SiC mirror，the 18-point supporting light-weighted structure is judged to be the preferred scheme at last. However,thermal deformation for SiC mirror is sensitive to the steady temperature difference. Referring to this problem, a measure that the supporting-structure design should be suited to the mirror thermal deformation is provided to achieve the design requirements.