With the increase in ambient temperature around the world in summer,the working environment of cable joints is deteriorating. Based on the finite element method,a simulation model for temperature analysis in a 10 kV three-core cable and the joints is established. The temperature distribution is analyzed under different ambient temperatures and different currents. Firstly,the temperature rise experiments are carried out to obtain a steady temperature on the surface of the cable joint,which verifies the accuracy of the simulation model. Then,the relationships between the surface temperature and the current of the high voltage current carrying conductor of the joint under different ambient temperatures are fitted. The ultimate safe current carrying capacity of the joint under the different ambient temperatures can be calculated by using these related functions. The results show that the increase of ambient temperature has little effect on the temperature distribution trend of the high voltage conductor surface of the joint,which also meets this rule on the outer surface of the outer sheath. The relation of the surface temperature on the high voltage conductor of the joint to the current is approximately a quadratic function. When the current amplitude is 480 A and the ambient temperature is 75 ℃, the highest temperatures on the surface of the high-voltage current-carrying conductor and the outer surface of the outer sheath are 1.57 and 1.69 times higher respectively than at an ambient temperature of 30 ℃. When the ambient temperature exceeds 55 ℃,the continuous allowable current carrying capacity specified in the national standard can make the high voltage copper conductor of the joint exceed the maximum permitted operating temperature of 90 ℃. Considering the continuous increase in summer ambient temperature since 2020,the continuous allowable current carrying capacity of the intermediate joint of 10 kV copper conductor three-core cross-linked polyethylene insulated cables in the GB needs to be improved and perfected.