Abstract: To reveal the effects of shear flow behaviors in grooves on the reduction efficiency of sliding resistance, theoretical analysis, experiments and numerical simulation were carried out using a static/dynamic sliding friction coefficient test system and computational fluid dynamic (CFD) method. The influence of groove sizes (aspect ratio of 0.5, 1, 2, and 3) and the velocity of sliding wall on the shear flow characteristics in grooves and the drag reduction efficiency of the sliding wall were investigated. It is found that the surface groove increases the drag reduction effect of lubrication oil, and the groove structure has significant influence on the drag reduction effect. When the width and depth are 2 mm, the groove has better drag reduction effect, and the wall sliding speed has low influence on the wall shear stress distribution. Moreover, the groove size and the wall sliding speed have important influence on the characteristics of the flow field in the groove. Under different working conditions, there are two or one large vortex and two corner vortexes in the groove. Results show that the shear flow behaviors in the groove have significant influences on the drag reduction effect, and can provide a useful guidance for the design of the groove for drag reduction.