The electromagnetic environment has gained much interest in recent years， especially power frequency electromagnetic field， as the development of domestic power grid. As for such an issue， a kind of improved algorithm based on charge simulation method is proposed in this paper， with which the holistic modeling is implemented and the electric field distribution at the height of 1.5m is identified via programming calculation. And the algorithm is proved to be of validity by comparison with simulation of CDEGS software. Eventually， the specific electric field of a 220kV substation distribution is calculated meanwhile three influencing factors are studied， which can be utilized as credible guidance for substation construction.