For requirements of the mirror in a space remote sensor for support function, a compound support structure used in the mirror with a large aperture in the space field was designed. The compound support structure includes a peripheral support composed of an A frame and a tangential pull rod and a back support composed of three groups of whiffletree structures. The support principle and engineering realization of the compound support structure were researched. Then, the design idea of function allocation and index allocation was used to design the compound support structure. The statics and dynamics simulations were carried out on the design result by the finite element analysis, and the relative test was performed on the actual mirror support component. Experimental results show that the surface shape error of the mirror with the compound support structure is better than λ/50(λ=632.8 nm), the rigid body displacement of mirror and the dip angle are smaller than 0.01 mm and 2″ respectively, and the mass of mirror component is less than 50 kg. Furthermore, the component has a reasonable modal distribution, and the fundamental frequency is 161 Hz, higher than the requirement of 120 Hz. The simulation and test results demonstrate that the compound support structure has good support effects, which meets the demand of space remote sensors for high reliability and high stability.