In the electric field calculation of transmission line mostly treat the ground which is under the lines as the ground so that ignore the influence of irregular ground to the electric field calculation; Thus, a three-dimension model to compute power frequency electric field surround the slope under the transmission line is built . According to charge simulation method, the distribution of power frequency electric field at ground and slope surface is analyzed, and the factors impacting computational results of electric field are discussed. Research results shows that there is a great impact on ground surface electric field nearby the slope. The effect is that close to slope toe, the power frequency electric field of EHV transmission is weakened and the field is strengthened with the height of the slope become higher, and the electric field distortion appears at the top of slope. Computation result of electric field will be impacted by the angle and altitude of the slope, the position of the transmission line between the slope, the density of the simulation charge of the transmission line .The larger angle, the higher height of the slope, the electric field distortion is become obviously. The angle of the slope and the power lines is more greater and the reducing of the electric field is moer abviously .