Abstract: In response to oxidation discoloration of copper conductors in cross-linked polyethylene (XLPE) insulated cables during chemical cross-linking process, main cause of oxidation was revealed through mechanism analysis: besides high-temperature environment, migration of peroxide cross-linking byproducts toward conductors was identified as primary trigger for catalytic oxidation. Based on this, a conductor-insulation collaborative protection system was proposed: on conductor side, high-temperature-resistant passivation with 0.3% benzotriazole (BTA) solution and semiconductive nylon tape lapping were applied; on insulation side, shielding material formulation was optimized; and at process end, multi-stage nitrogen protection and precise control of cross-linking parameters were implemented. Industrial verification showed that conductor oxidation rate was reduced by 92%, and a dual theoretical-technical solution was provided for the industry.