Abstract: A three-dimensional, time-dependent,and self-consistent fluid model is developed to simulate the helium plasma in a cylindrical microhollow cathode (MHCD) with reasonable boundary conditions. The particle density, electric potential, electron energy,and the distribution of the electric field are calculated. The results show that there exist the cathode dark space region, negative glow region,and the hollow cathode effect is in evidence. The results presented in this paper provide an understanding of the basic mechanisms governing the MHCD devices.