Abstract: The discharge plasma in the rectangular micro hollow cathode (RMHCD) under high pressure has a multiple negative glow region structure, and the negative glow regions have a tendency of fusion, which can significantly increase the ionization efficiency. The gas is confined in the cavity, which can be effectively heated, and thus can be applied to micro-electric plasma thruster (MPT). In this paper, the 2D x-y cross-section of a rectangular micro-discharge plasma thruster (RMPT) is simulated and analyzed, and a self-consistent fluid model with non-equilibrium state is adopted in the method. The ion current heating and the three-body collision are also considered. The results show that the RMPT has two stable negative glow regions under low current conditions. When a certain current threshold is exceeded, the two negative glow regions will merge at the center of the cavity. Corresponding analysis suggests that the fusion process is essentially a hollow cathode conduction process, whether or not the fusion of negative glow regions occurs is related to sheath voltage.