A coupling model of electromagnetic field, thermal field and fluid field of high-voltage cable terminal is proposed in view of the low accuracy of existing single physical field model and couple coupling model in judging the defects of power cable terminal. The electric thermal field characteristics of 220 kV high-voltage cable terminal defects are analyzed. By using the multi-physical field simulation software tool COMSOL, the electrical thermal field characteristics of high-voltage cable terminal defects (local water ingress and oil leakage) are analyzed. The results show that the local water ingress defect of the cable terminal will lead to local heating of the terminal and varying degrees of electric field distortion. There is no obvious temperature rise on the surface of the cable terminal oil leakage defect, and the electric field distortion in the cavity formed by oil leakage is obvious, which will lead to insulation breakdown in serious cases. In practical application, the error between the model result and the actual value is about 1%. This study provides theoretical support for the early diagnosis of internal defects in high-voltage power cable terminals.