Abstract: Based on a simple cubic lattice, a 3 - D network model with regular or random structures and periodic boundary was established. In this model, the pore structure is assumed to have a "chamber throat" geometry and pore sizes obey Weibull distributions. Using such a network model, the isotherms of nitrogen adsorption and desorption in porous media were simulated for various coordination numbers and different ranges of pore sizes. The effect of geometry and topology of the network model on sorption hysteresis was studied in particular. The simulation results showed that the main factors that affect the shape of sorption hysteresis are the radii of throats and the coordination number of network model.