Understanding of multiphase flow in porous media is of interest to many areas of science and engineering since it has a number of practical applications in well known areas, such as fuel cells, hydrocarbon recovery, hydrology, filtration, CO2 storage and catalyst reactors. Even though significant effort has been dedicated to unravel the phenomena associated to flow in porous media, there are still many open questions concerning the flow dynamics and associated pressure drop. For example, in many cases, liquid phases are disconnected by gas or bubbles. When a gas-liquid mixture is pumped through a porous medium, the pressure drop oscillations can be observed. In this paper, we experimentally investigate the impact of gas-liquid interface on two-phase flow in porous media, and the impact of the gas phase on the pressure drop. The effect of solution pH and pore size on the impact of gas-liquid interface is presented as well. The results show that the gas phase resulted in a significant increase in the pressure required to drive the gas-water interface through a pore throat. The pressure required for driving water through the pore and pore throat was 0.01 bar at a flowrate of 0.01ml/minute. However, when the gas phase approached the pore throat, the pressure increased significantly from 0.01bar to 0.027 bar. The resistance of pore throat on the two-phase interface not only depends on the capillary force and viscosity, but also increases greatly with the displacement of gas-liquid interface in pores. This resistance from the introduction of gas phase is independent of bubble volume.