The large aperture primary mirror assembly (PMA) mounted in space remote sensor should have the extraordinary virtues as high stiffness, high strength, high thermal stability etc.. A novel three-point flexural support configuration based on Cartwheel flexural hinge for large aperture PMA is presented in this paper. Firstly, the stiffness characteristic of the support structure is approached using the dimensionless design method. Then, static and dynamic analysis based on finite element method are performed on the PMA to find the optimal dimension parameters of the support flexure. Finally, optical test on a mirror with λ/40 root mean square (RMS) surface figure and vibration experiment on an equivalently spherical mirror are performed to validate the design configuration. The simulation and experiment results indicate that when the thickness of flexure t=8 mm, beam height h=4 mm, beam length L=8 mm, the surface figure of PMA can keep below RMS 12 nm under the load of 1 G gravity and 15 ℃ temperature change. The first natural frequency reaches 296 Hz, only deviating 6% from the analysis result. The Cartwheel flexure support can satisfy the extraordinary design requirements.