The work aims to verify the protective effect of SiO2 coating on the atomic oxygen erosion resistance of PEI insulation materials. With PEI insulation material of electrical connector selected from the cabin of a spacecraft as the research object and PHPS as the coating material, KH-AORX liquid phase coating method of bottom coating and surface coating was used to directly convert PHPS into silica (SiO2) inorganic protective coating. Based on the requirement of 15-year service life for the model in orbit, a 5-year experiment with total atomic oxygen flux of 2.61×1026 atoms/m2 and the atomic oxygen flux rate of 6.5× 1015 atoms/(cm2.s) was carried out. The changes of material mass loss rate, atomic oxygen denudation rate and appearance before and after the experiment were analyzed. KH-AORX liquid phase coating method could make PHPS coating material act on PEI insulation material and directly convert it into SiO2 protective coating. The edge thickness and center thickness of the coating had good consistency, and the hardness and adhesion of the coating met the design requirements. The mass loss rate of PEI insulator coated with SiO2 was 0.05% after 5 years of atomic oxygen denudation, and 0.29% after 15 years of atomic oxygen denudation after fitting calculation. According to the electron microscope examination, the SiO2 coating on the surface of PEI insulator showed no delamination, peeling and substrate exposure. Using KH-AORX liquid phase coating method to convert PHPS into SiO2 coating on PEI insulation material can obtain a large film with uniform thickness distribution. The SiO2 coating can effectively protect the atomic oxygen resistance of PEI insulation material, and meet the on-orbit service life requirements of extravehicular application.