Abstract: La₂O₃–Mo, Y₂O₃–Mo, Gd₂O₃–Mo and Ce₂O₃–Mo were prepared by liquid–liquid doping combined with spark plasma sintering. The microstructure and surface behaviour of rare earth oxide of the cathode have been studied by microscope, Auger Electron Spectroscopy (AES) and X-ray Photoelectron Spectroscopy (XPS) methods. Among these four kinds of cathode, Y₂O₃–Mo cathode exhibits the best secondary emission property, i.e., the maximum secondary emission yield could reach 5.24. The penetration depth of primary electrons and escape depth of secondary electrons have been calculated and the energy distribution of primary electrons in the cathode has been simulated by Monte Carlo method. Y₂O₃–Mo cathode has the largest penetration depth and escape depth, which could be attributed to the highest secondary electron emission yield of the cathode.