Abstract: A method for evaluating the repair effect of buffer layer ablation in high voltage cables based on impulse voltage is proposed. By introducing the capacitance current variation rate, quantitative assessment of the repair performance is achieved. An equivalent circuit model of the buffer layer in cable is established. The effects of ablation degrees, ablation products type and repair agent injection ratio on the capacitance current response characteristics of the the buffer layer are analyzed. As the sodium carbonate content increases from 0% to 70%, the peak capacitance current decreases from 0.70 A to 0.46 A, indicating that increased ablation severity weakens the conductive capability of the buffer layer. Meanwhile, mixed ablation products exhibites stronger high-resistance characteristics. Buffer layer samples with different repair agent injection ratios are prepared. As the injection ratio increased, the peak capacitance current increases by up to 31.3%, indicating that the repair agent helps restore the electrical connection condition of the buffer layer. By comparing the capacitance current responses before and after repair, quantitative evaluation of the repair effect can be achieved. In long-distance cable engineering tests, the peak capacitance current is found to increase by 41.7% after repair, indicating that the method may have practical applicability and reference value in engineering applications.