There are rigorous requirements on the characteristic of electron beams in Free Electron Laser(FEL) operation, such as high brightness and high average current. High voltage DC electron gun with photo-cathodes has become the first choice for generating the beams. A high voltage DC electron gun is designed to work stably at 350 kV. The software of the control system is developed in VC++ 6.0 for DC gun. The experimental results indicate that the control software can be operated easily with friendly interface and rapid response speed. It can provide support for the high-voltage aging of electron gun and system evaluation due to its good reliability and stability.