Research conclusions:(1) When the length of Metro station is less than 200m，one step － down substation can meet the needs of power distribution，but for the station with narrow platform and being difficult to install the cable bridge or rack，two substations should be built．(2) When calculating the electrical load，the reasonable coefficient should be chosen for the intermittent load according to the operating mode，and some fire equipment loads should not be counted in the total computational load for the scientific choice of transformer capacity．