Using the lightning path taken by the high speed camera and the simulated lightning path, the electric field peak errors are analyzed by assuming the lightning path being vertical. The results show that at close distances, the field waveform is dependent strongly on azimuth; at distance of several hundreds, the ratio of the peak error values at two azimuths may be bigger than 2; at the distance of 1 km, the mean error is less than 10% with a maximum value of 50%.The calculated relative error decreases with the increasing of distance.