Abstract: The turbulent flow in a channel with superhydrophobic surface was studied by numerical simulation， and the drag of the surface was analyzed. We applied structural grid to grid the field，and VOF model and Realizable k-εturbulent model to make the simulation. It shows that: the wall slip and low turbulent enerage near the wall are the importment factors that make the drag of hydrophobic surface reduced; the volume of the air in the cavity influences the drag of superhydrophobic surface obviously, however, the drag reduction still exit even if the cavity were full of water.