The different arrangement of the cables will affect the distribution of its temperature field, which will affect its current carrying capacity. In this paper, the combined simulation model of temperature field of distribution cables laying in 3*4 pipes is established by COMSOL and MATLAB, and the layout of multi cables applied equal current is optimized under the rule of the temperature of the hottest cable in the group being the lowest. Based on the simulation of the cables temperature under all the layouts of the multi-circuit cables, the optimal layout of the cables and the cable newly added to the group are finally determined. The results show that the optimization of cable group layout can significantly improve its current carrying capacity and reduce its operation temperature, which is of great significance for the long-term safe and economic operation of the cable.