Abstract: In order to meet the design requirements of 750 kV cross-linked polyethylene insulated power cables, specific indicators and calculation methods for insulation micropores, impurities, and interface protrusions are proposed. Through the breakdown field strength test and Weibull distribution analysis of ultra clean XLPE insulation material, the influence of the uniformity of insulation impurity distribution on insulation reliability was verified. Based on the power frequency breakdown field strength and impact breakdown field strength, and according to the principle of the same reliability, the insulation thickness of different conductor cross-sections was finally determined. This article briefly describes the production process control of 750 kV cross-linked cable insulation and the application of domestically produced ultra clean insulation materials, providing guidance for the research and application of 750 kV cross-linked cables.