The dynamics of a liquid droplet driven by an air flow and displaced on the micro-grooved surface was investigated, and a force balance model in terms of dynamic contact angle was obtained. Two terms of θ(α) and r (α) were improved in the calculation of capillary force. The term θ(α) was expressed by a piecewise function while term r (α) was deduced by the equation of elliptical contact line. The drag force was simplified by importing the no-slip boundary condition. Then the model was tested in a wind tunnel experimentally. The test results turned out to be consistent with the experimental results, which proved that the force balance model was rational and effective.