The charge simulation method is one of the most important means to calculate and analyze the electric field of UHVDC transmission line. This article takes the relative error of the electric field on wire surface as a criterion to analyze and optimize the location and number of simulation charge

and compared this method with the conventional method in which the relative error of voltage on wire surface is used. The results show that when the simulation charge distributes evenly in the sub-wire concentric circle with a radius of 0.61 times of the sub-wire radius and when the charge number is 12

the proposed charge simulation method becomes optimal. The optimized charge simulation method can get higher accuracy in calculating the electric field

compared with the adaptive charge simulation method.