Permeability and porosity of the sandstone reservoir will change during the waterflooding process which is of great importance to the development of the reservoir.In this paper，we establish a pore scale network modeling method to simulate the formation parameter variation by taking different microcosmic particle variation mechanisms into account such as particle release，particle capture and particle migration in pore-throats.The simulations are conducted to study the formation parameter variation patterns under various conditions.The simulation results indicate that，after a long period of waterflooding，the pore-throat radius distribution has a small change，and the mean pore-throat radius will increase for the reason that part of particles would release from the pore-throat surface and flow out of the formation.During the waterflooding process，the permeability and porosity of the model increase gradually and stays almost steady after a long period.The water injection intensity and bond strength of clay particles will have an influence on the amplitude of variation by affecting the release rate of particles.