Abstract: Aiming at the problem of distortion of test results in the process of X-ray photoelectron spectroscopy etching analysis, the CaF₂ sample was taken as the research object. The test results of oxygen content on the surface of the sample were analyzed by changing the parameters such as ion beam energy, pause time after etching, and fine spectrum scanning sequence of oxygen elements. At the same time, SRIM software was used to simulate the vacancy defects generated by argon ion beam etching of CaF₂, which provided data support for test distortion analysis. The results show that the oxygen element measured on the surface of CaF₂ was due to the adsorption of hydroxyl and O₂ in the residual gas on the surface of the sample. By optimizing the X-ray photoelectron spectroscopy test parameters, the surface hydroxyl and adsorbed O₂ could be effectively removed, and the influence of residual gas on the test results could be weakened or eliminated. The polar molecules and low surface binding energy of the material were the main reasons for the rapid adsorption of residual gas on the surface during ion etching. The research results had important guiding significance for the accurate characterization of the elemental composition of polar molecular materials by X-ray photoelectron spectroscopy.