The influence of the outer skin assembly deviation， self-weight， forming and service temperature difference on the profile accuracy especially the R.M.S value of reflector working face is specially analyzed. The results show that through 0.5mm assembly offset of the outer skin， the reflector working face theoretical R.M.S value changes 0.47μm. Under the forming and placing condition， the 11kg self-weight has 0.55 μm deviation on the theoretical R.M.S value of the reflector working face. The temperature difference of it between the forming and service the reflector brings 17.79μm change of the theoretical R.M.S value.