本文用电解槽模拟,采用逐次放大逼近阴极尖端的方法,克服场发射枪系统阴极附近电场激剧变化及尖端与阳极尺寸上的巨大差异所引起的计算电场的困难,获得实际阴极附近足够精度的电场分布。并由此计算得到沿阴极表面亮度分布。从模拟得到的阴极区域电子轨迹,获得虚源大小及位置与电子束发射角有关的结果。 In this paper, we simulate the electrolytic cell and approach the cathodic tip one by one to overcome the difficulty of calculating the electric field caused by the drastic changes of the electric field near the cathode of the field emission gun system and the sharp difference between the tip and the anode, and obtain the sufficient accuracy near the actual cathode Electric field distribution. The brightness distribution along the cathode surface was calculated. From the simulated electron trajectories in the cathode region, the results of the virtual source size and position related to the electron beam emission angle are obtained.