In order to solve the problem of insufficient calculation accuracy in existing high?voltage XLPE cable thermal evaluation models under continuously fluctuating loads, this paper explores the traditional methods (including IEC 60853?2 and thermoelectric equivalent method) using constant insulation layer heat capacity distribution coefficient, and the accumulated calculation errors are investigated when subjected to continuously fluctuating loads. An optimized approach for the lumped thermal model of cable insulation is proposed to mitigate potential error accumulation. The proposed improved thermoelectric equivalent(TEE) method is validated through the dynamic cable temperature rise experiments. The analysis reveals that the improved TEE method can better predict the real thermal performance of cables under continuously fluctuating loads, with conductor temperature calculation errors being maintained within 2.5 ℃. The methodology developed in this paper paves a way for electricity utilities to enhance cable utilization while ensuring cable reliability.