The methods and devices which can be used to determine the wettability and zeta potential of filter medium were developed according to the principles of capillary rise and streaming potential respectively. Lipophilic Hydrophilic Ratio (LHR) was defined based on Washburn equation. LHR values and zeta potentials of some conmen filter media were measured respectively, and the oil removal efficiencies of these filter media were also tested. The result shows that the effect of wettability on oil removal efficiency is much greater than that of zeta potential in conmen condition. The oil removal efficiency mainly depends on LHR value of filter medium, not on zeta potential of filter medium.