In view of the water seepage of electric power pipes due to short-term waterlogging and the water accumulation of cable pipes caused by blocked drainage channels, this paper takes distribution network cable groups as the research object, and based on IEC60287, constructs an improved equivalent thermal circuit model of cable system considering the impact of water accumulation on the heat exchange in the pipes, and calculates and analyzes the current carrying capacity when there is water accumulation in the pipes based on the unequal load optimization algorithm, The influence law of different water accumulation depth on the current carrying capacity of cable group is revealed. The results show that the current carrying capacity of the cable laid in the drain pipe increases with the increase of the water accumulation level. When the water accumulation level completely submerges the cable, the increase rate of the current carrying capacity of the cable slows down.