Abstract: The space charge around ultra high voltage dc transmission line makes the electric field distribution nearby complicated, and has an effect on the insulator flashover nearby. The ion flow field near the 500kV single-electrode high voltage dc line is simulated based on the upper-class finite element method in this paper, and an iterative convergence control algorithm is adopted to ensure iterative convergence. The influence of space charge on the surface electric field parameters of 500 kV dc insulators is studied.