In view of the frequent occurrence of 10 kV power cable joints burning accidents, the heating analysis and safety monitoring of the power cable joints are studied. Based on the current situation of railway power cable maintenance, a simulation model of the cable joints temperature field is established by finite element analysis method. By analyzing the distribution of cable joints temperature field under actual working conditions, it is found that excessive traction ground backflow in the metal sheath has great influences on the heat dissipation of main insulation, and abnormal temperature rise points will be formed at the cable joints when the contact resistance is abnormal. On this basis, the least square method is used to process the temperature field simulation data, and the formula for setting the maximum current carrying value of the cable and the temperature threshold value of the outer sheath is obtained, which provides a theoretical basis for cable load adjustment and safety monitoring. Finally, an on-line monitoring device based on the measurement of state quantities such as cable sheath temperature, grounding wire current and main insulation dielectric loss tangent value is researched and developed to realize real-time monitoring, abnormal alarm and accident hidden danger warning, and to provide decision-making basis for the maintenance of the cable joints. This work is supported by Key Research and Development Program of Shaanxi Province (No. 2018ZDXM-GY-169), Xi’an Science and Technology Project (No. 2017080CG/RC043(XALG026), and 2019 Science and Technology Technical Service Project of State Grid Shaanxi Electric Power Research Institute (No. 2019-4-044).