In order to indirectly measure the hot spot temperature of the conductor core of the soil buried cable intermediate joint, the three-dimensional of the electromagnetic-thermal multi-physical field coupling simulation model of the cable intermediate joint was established by using COMSOL simulation software. Based on the thermal conductivity of soil and its temperature and load current changed, the temperature distribution characteristics of cable intermediate joints were studied by the multi-physical field coupling simulation model. Firstly, the equivalent thermal circuit model of the cable body and its intermediate joint was established, and the overall thermal circuit model was constructed by using the axial thermal resistance. After that, the surface temperature of the cable body and its intermediate joint were taken as the input to calculate the hot spot temperature of the conductor core of the cable intermediate joint. The results show that the influence of load current on the hot spot temperature of conductor is significant and increases exponentially, followed by the influence of soil thermal conductivity, and the influence of soil temperature is relatively small. The average error of the calculated temperature of the finite element model and the thermal circuit model is 1.89 ℃, which verifies the accuracy and universality of the combined thermal circuit model. The research results can realize the indirect measurement of the conductor temperature of the buried cable intermediate joint, and provide an effective reference for the real-time prediction of its insulation state.