Abstract: In electron beam lithography system,focus ion beam system and cathode ray tubes,the space charge effect caused by the interaction of every particle affects the quality of the device.A lot of scholars have already studied the space charge effect.As so far,Monte Carlo method is often used to calculate the space charge effect in the transportation of particles.This paper tries to use Monte Carlo method to calculate the space charge effect in the beam form region.The 'edge effect' is analysed and some new ways are proposed to decrease the'edge effect' in the simulation.

Key words: Monte Carlo method, beam form region, edge effect, effeciency of calculation