According to the load features of low load density area, put forward use 20kV as medium voltage in this area.Consider from the furthest distance of power supply,reach the measure of confirm the number of outlet,constructed a power grid model which fit the low load density area,on this basis,use the annual cost as object function put forward the economic analysis mathematical model in low load density area,and then compare with the technical and economic characteristics of different voltage level,verify the feasibility of the 20kV voltage levels in low load density area.