Using the four-equation of linear spring-dashpot discrete element method and considering effect of the liquid bridge, the mixing and segregation process of size-type binary wet particulate system in a rotating horizontal drum is simulated. The effect of interstitial liquid on the mixing and segregation process is discussed. To assess the accuracy of the simulation result, some comparisons are made with the experimental date in the literature. The simulation results show that the liquid bridge between particles plays an important role in mixing and segregation process, and that the cohesion force induced by liquid-bridge leads to the formation of agglomerates of particles. As a result, segregation may be mitigated and mixing may be enhanced, and the network distribution of the contact forces is more uniform in wet particulate system.