Abstract: In order to study insulation thermal stability of thermoplastic polypropylene (PP) insulated medium voltage power cables, short-circuit test was carried out on PP insulated and and cross-linked polyethylene (XLPE) insulated medium voltage power cables with a conditional temperature of 250 °C and short-circuit time of 1~7 s. Structural size, mechanical and physical properties, and electrical properties of PP insulation and XLPE insulation before and after short circuit test were tested and analyzed. Results showed that structural size, mechanical and physical properties, and electrical properties of PP insulation and XLPE insulation had no significant change before and after the short-circuit test, which was that PP insulated medium voltage power cables had the same short-circuit capability as XLPE insulated medium voltage power cables. Research results could provide data support for application and promotion of PP insulated cables in the field of transmission and distribution, and also provide research direction for development of PP insulated medium voltage cables in industry manufacturing enterprises.