In view of the significant impact of the initial substation site on the planning results for the substation planning， a new algorithm is proposed to automatically search rational initial substation sites. First， according to the possible number of substations， the planning region is meshed redundantly with the center of a grid as a candidate for the initial substation site. Then， the number of substations should be reduced one by one based on the principle that a substation should preferably be located near the load center and the method of discarding the smallest loading substation to find the initial substation sites for the cases of different substation numbers. The factor of distance weights is employed to balance the loading of individual substations. A method for alternation of substation locating and sizing is employed to find the size and location of potential cases， and the optimal one is selected from those cases to rationally avoid the local optimal solution. Numerical examples show that the proposed algorithm can stably and quickly yield better planning results.