With the development of cities and electric power industry, the demand of electrical energy, generation, transmission, distribution and the voltage levels have increased considerably. Therefore the power frequency electric field and environmental impact assessment near / under the high voltage overhead busbars, incoming and outgoing feeders inside the high voltage substations (HVS) have caused wide public concern. Nowadays most research on electric field are concerned with calculation the electric field distribution around the transmission lines, insulators and cables but they rarely concerned with its calculation inside HVS. In this paper, a different type of calculation is achieved, the charge simulation method (CSM) is employed to analyze the three dimensional (3-D) electric field distribution near / under the busbars, incoming and outgoing feeders. At last, the effects of changing the level of operating voltage, the space between the phases, the level of calculation inside HVS is demonstrated.