Abstract: In order to reduce the effect of the assembling process on the accuracy of the surface shape of the mirror, based on a space camera's mirror subassembly, a flexible support structure was designed, and the assembling method was formulated. First, the thickness and the area of the adhesive, the flexible hinge as well as other parameters were given based on the formula. Second, the finite element analysis for the mirror subassembly was carried out under the combined effect of gravity and 5 ℃ temperature change. Third, according to the assembling process of the mirror subassembly, the viscose and curing treatment for the mirror subassembly was carried out. Finally, mechanical test and thermal vacuum test of the mirror assembly was conducted so as to verify the alignment method. Experimental results indicate that, under the mechanical and thermal vacuum environment the viscose of the mirror subassembly is not destroyed, and the accuracy of the surface shape of the mirror is better than 1/50 . It can verify the effectiveness of the mirror support structure and assembling method for the mirror subassembly.