Abstract: In this paper, a novel high current diode with multipacting cathode is studied and verified by using simplified dynamic theory and Monte Carlo simulation. Firstly, based on the design-prototype and the emission characteristics of secondary electron, the dynamic model is established, the expressions of electron velocity, displacement and transit time are obtained from the simplified dynamic equations. The multipacting cathode's working range (multipacting susceptibility) is obtained, by using dynamic theory and Vaughan's SEY (Secondary Electron Yield) model. Secondly, the importance of the applied electric field in radial direction is discussed, and the characteristics parameters of moving secondary electrons are analyzed theoretically, such as maximum displacement, transit time, and impact energy. Finally, the novel high current diode with multipacting cathode is investigated by using Monte Carlo simulation in detail. The physical images of secondary electron's trajectory, impact energy and the multipacting working range diagram are analyzed and discussed. The theoretical results are verified by Monte Carlo simulation and they agree with the theoretical results. The possible reason of the error between theoretical and simulated results is discussed. Both theoretical and numerical results demonstrate that the concept of the novel high current diode is feasible, by adjusting the magnitude of the applied electric field and magnetic field, the moving status of secondary electrons could be controlled effectively. Under the condition of multipactor saturation, the roughly theoretical estimation indicates that the novel multipacting cathode has the performance of high emission current density, and the emission current density can run up to the level of ~kA/cm². Enhancing the magnitude of applied electrostatic field in radial direction can effectively improve the emission current density. In addition, the design procedure of the multipacting cathode is introduced and discussed in detail.