Abstract: According to the interaction between two phases of liquid and solid, put forward a mechanism of liquid slipping along solid surface. When the flow rate of the liquid slipping along the solid surface exceeds that of a critical speed, slipping will occur and drag reduction will be realized consequently; otherwise, the liquid and solid will have an identical critical speed. The smaller the power of adhesion between solid and liquid, the greater the viscosity of the liquid, and it is easy to realize slipping drag reduction with a smaller critical flow rate, and put forward a concrete recommendation for slipping drag reduction.