Abstract: Flow characteristics of horizontal two-phase gas-liquid stratified flows with low liquid loading are studied through both air-water and air-HVIW base oil experiments on the large-scale multiphase experimental loop. Based on measurement and observation of flow pattern, "apparent rough surface" (ARS) model is selected to calculate frictional pressure gradient with gas-liquid momentum balance equations. The predictions of the models are compared with the data measured in the experiment. Some results of pressure gradient are obtained, so ARS interfacial shape is recommended in horizontal two-phase gas-liquid flows with low liquid loading.