Based on the boundary layer theory in this paper，a theoretical model for the coupling problem of two phase boundary layer of gas and droplet has been established. A formula to calculate the minimum velocity of gasflow needed to start the aerodynamic stripping has been obtained for the problem of the aerodynamic stripping，which is a result from the interaction between gas and a droplet surface when the droplet is in a high speed gas flow. This paper could be a useful to the investigation of atomizing mechanism of liquid fuel in high speed gas flow.