With the improvement of buried power cable load refinement management level, accurate calculation of cable core temperature rise of direct buried cable group and accurate assessment of its current carrying capacity are of great significance to improve the utilization rate of power cable assets and the safety and reliability of power cables. The relationship between the thermal conductivity, specific heat capacity, density and water content of the soil is obtained experimentally; the electromagnetic-thermal coupling model and the thermal-hydraulic migration coupling model of the soil area are constructed to realize the multi-field coupling calculation of electromagnetic-thermal-hydraulic migration of the whole field; the relationship between the temperature of the cable core and the load capacity of the direct buried cable before and after considering the hydraulic migration, and the influence of the burial depth and the initial water content on the temperature and load capacity of the cable core are studied. Simulation experiments show that water migration is obvious when the direct buried cable is working for a long time, which will cause the cable temperature to rise and load capacity reduction.