Abstract: The main reason of AC loss of cable is the skin effect and proximity effect, which can be effectively reduced by reasonable design of cable section. Based on the research of skin effect, a theoretical formula for calculating the proximity effect of profile cable is proposed, and then an analytical method for calculating the overall AC loss of profile cable is obtained. Compared with the corresponding simulation results, the correctness of the proposed method is verified. On this basis, the method is used to calculate the AC/DC loss ratio of S-type cable under different section structure parameters, and the relationship between section shape and size and AC loss is analyzed. The results show that the current density distribution calculated by the proposed method is in good agreement with the software simulation results; through the reasonable design of S-shaped section, the AC loss can be greatly reduced. The results provide reference for the design of cable structure.