Abstract: Pseudospark discharge is a kind of special low pressure discharge which works in the left half branch of Paschen curve. It has important applications in gas switch and electron beam sources. When the pressure is low, the potential barrier will be formed at the cathode hole at the end of the hollow cathode discharge stage, which will hinder the outflow of electrons in the cathode cavity and thus hinder the further development of discharge. In order to study the formation process of potential barrier, particle simulation and Monte Carlo collision method (PIC/MCC) are used in this paper to establish a two-dimensional electrostatic plasma simulation model coupled with external circuit elements. By studying the variations of electric potential and charge in the cathode hole area, it is found that when the virtual anode is formed at low pressures, the electric potential at the cathode hole decreases rapidly, which accelerates the outflow of electrons in the cathode hole until the electrons are exhausted and finally forms the electric barrier. The simulation results show that increasing gas pressure can effectively increase the number of electrons, ions and the probability of collision ionization of electrons in the cathode hole, so that the formation time of the barrier can be continuously pushed back or even completely suppressed. After the formation of the virtual anode, the collision ionization in the cathode hole is mainly maintained by a large number of free electrons generated during the discharge stage of the hollow cathode, and the effect of secondary electron emission on the electric field establishment of the virtual anode and sheath layer is only 20%.