Abstract: Amidst the escalating global energy crisis, there is a growing scholarly focus on flow reduction. The composite structures of superhydrophobic microchannels facilitate the formation of gas-liquid interfaces, consequently achieving drag reduction. Nevertheless, the drag reduction characteristics of composite structures in hydrophilic microchannels remain uncertain. This study integrates numerical simulation and experimental research to explore the drag reduction properties of three surface composite structures: transverse post structure (TPS), doubly reentrant transverse post structure (DR-TPS), and doubly reentrant surface groove structure (DR-SGS). Our investigation reveals that under stable gas-liquid interface conditions, all three structures demonstrate drag reduction properties. Notably, TPS and DR-TPS yield similar drag reduction effects, while DR-SGS exhibits the most significant drag reduction effect, reaching a maximum reduction rate of 11.8%. Simulation results indicate that the drag reduction effect of TPS and DR-TPS is inferior to that of DR-SGS due to localized drag increase caused by vortex structures within the flow field. Additionally, the flow rate impacts the drag reduction effectiveness of the three structures. Higher flow rates make the gas-liquid interface within the structure susceptible to collapse, thereby diminishing the drag reduction effect and potentially leading to increased drag. Furthermore, the sequential increase in the ability of TPS, DR-TPS, and DR-SGS structures to maintain gas-liquid interface stability is observed.