Abstract: By introducing fluid-fluid and fluid-solid surfacesinteractions, the process of the non-wetting vapor phase displacing complete-wetting liquidphase in two-dimensional pore-networks is simulated based on the Shan-Chensingle component multiphase model of lattice Boltzmann method. The fluidinterfaces form naturally and the displacement is of capillaryfingering. With the capillary number increasing, the viscous forcebecomes more and more dominatingand the sizes of the pores invaded by vapor decrease, leading to richbehaviors of the displacement. With the imposition of the gravity, thegravity plays a stabilizing role on the vapor invasion front.