Abstract: According to the characteristic of flow field of riblet surface, microcosmic flow field of riblet surface was studied thoroughly through experimental measurement and numerical simulation. Distribution of mean velocity, distribution of turbulence intensity and microstructure of turbulent boundary layer of riblet surface were obtained. To understand the effect of structure of riblet surface on properties of wall, the apparent contact angle of riblet surface was measured and drag reducing effect of riblet surface was confirmed by water-tunnel experiment. The results showed that compared with smooth surface, there was secondary vortex in micro flow field;, the viscous sub-layer in the near region of riblet surface was thicker; turbulence intensity was depressed and riblet surface was hydrophobic. Finally, the drag reduction mechanisms based on wall separating effect, increasing turbulence damp effect and altering wall character effect were proposed.