Abstract: Cold cathode RF electron guns based on field emissions combine the characteristics of thermo- and photo-cathode RF guns and may provide low emittance, high current electron beams. Studies of such a gun in the Institute of Applied Electronics, CAEP are presented here. The effective work function of diamond films is greatly reduced by doping so that valuable electron currents can be obtained at the presence of moderate electrical field strengths. A test RF gun was designed by taking into account many factors such as back-bombardment and accelerating efficiency. Particle tracking of such a gun was implemented and turned out that low emittance electron bunches can be obtained at the gun exit. However, the energy spectrum is not so good and needs improvement in the future.