Abstract: Regarding oxidation phenomenon on copper strip shielding inner side of medium voltage power cables, the oxidation mechanism including electronic structure of copper atoms and common types of oxidation reactions were analyzed. Factors influencing oxidation such as atmospheric conditions and manufacturing processes were explored. And the causes of oxidation on copper strip shielding inner side were investigated. Using the control variable method, the oxidation behavior of copper strip shielding after contact with insulation shielding and cooling water were analyzed. Results showed that copper strip itself had certain anti-oxidation properties, its oxidation was accelerated by temperature and by-product gas release during the plasticizing process of shielding material. To further understand products and causes of copper strip oxidation, an abnormal cable was dissected for comparative analysis of the inner oxide composition of copper strip, surface residues on the cross-linked core, and composition of the cross-linked circulating cooling water. Infrared spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis revealed the presence of N-(2-hydroxyethyl) stearamide organic compounds, Zn and Cu in the inner oxide layer of copper strip. Through macroscopic testing and microscopic elemental analysis, it was concluded that under the combined effects of the humid environment provided by the outer screen of crosslinked wire core and the acidic environment from cooling water, chemical corrosion occurs in the presence of temperature, humidity, and anions, accelerating the formation of copper oxide and leading to oxidation and discoloration of the inner copper strip. Based on current research findings, optimization strategies and rational use of antioxidants and other preventive measures were proposed.