Abstract: The gel-casting of reaction bonded silicon carbide, which is a material of space mirror, was processed by organic precursor impregnation. A silicon carbide ceramic component with fine secondary -SiC distributed uniformly in the matrix was prepared. The density and the microstructure in the impregnation process were investigated. The density of the sample without impregnation process was 2.945 g/cm3 after reaction sintered. Density increased to 2.969 g/cm3 after one time impregnation, and increased to 3.011 g/cm3 after two times impregnation. The proportion of fine SiC in microstructure went up with the increasing of the impregnation times. In which the reaction sintered process, the carbon introduced by impregnation and silicon reacted to form fine -SiC dispersed in matrix. Bending test was conducted for the samples. The bending strength of the sample without impregnation process was 308 Mpa. Bending strength increased to 339 Mpa after one time impregnation, strength increased by 10.1%, and increased to 380 MPa after two times impregnation, strength increased by 23.4%, which improve the mechanical properties greatly.