The evolution of saturation and liquid distribution in the filtration process of oleophobic coalescence filters were investigated. The effect of a drainage layer on the oleophobic filters with different layers was also evaluated experimentally. It was found that the wet pressure drop, saturation and liquid distribution were varied by assembling a drainage layer outside of the coalescing layer. For the filters with a non-wettable drainage layer, the pressure drop developed in the same fashion as the filters without a drainage layer. A secondary rise in the pressure drop occurred in the filtration process of the filters with a wettable drainage layer. For the filters with the same layers, assembling a drainage layer increased the flow resistance to liquid in the channels, resulting in an increase in the single channel size but a constant in the number of channels per layer. Moreover, the feature of channels in the coalescing layer was affected in varying degrees by the drainage layer, according to the location of filter materials in the filters. It was demonstrated that the middle filter materials were less susceptible to the drainage layer. In addition, there was less effect of a drainage layer on the liquid flow in the filters with more layers.