In this paper, the process of glow discharge in magnetron sputtering is studied by the particle-in-cell with Monte Carlo collision method. The proposed model is a two-dimensional and self-consistent approach. The results show that the discharge mode transits from the negative space-charge-dominated mode to positive space-charge-dominated mode with working pressure increasing or magnetic field weakening. At the transition state, working pressure and magnetic field are 0.67 Pa and 0.05 T, respectively. Discharge current increases as the cathode voltage increases. When pressure increases, discharge current first increases and then tends to balance. When the pressure is higher than 2.5 Pa, current begins to decreases with the increase of the pressure.