When submarine cable transmits electricity to onshore step-up stations,the ampacity and temperature rises of cable have close relationship with reliability in each path section laying mode,the accurate computation of the ampacity of conduit cable and distribution of temperature field has significance for the reliable and economical operation of power grid.This article combined with cable laying condition,With the use of COMSOL multi-physics software,this paper built a multiple physical field coupling model based on electromagnetic field, fluid field and heat transfer field,which simulates ampacity and temperature distribution.The simulation results show that the cable ampacity relies on the concentration degree of cable bundle,and irregular laying positions and overly dense loops can reduce the ampacity.Therefore,it is necessary to follow the procedures requirements to lay cable bundles and determine the appropriate number of loops,which can enhance operational economical efficiency.