Abstract: The paper presents the interactive motion equation ofinflatable structure in flow. The inflatable structure is used in thetechnique of a variable leading edge for high lift. The interaction betweenstructure and fluid is a typically aeroelastic problem. The motion equation isobtained through the analytic solution of an infinitesimal element in thediscrete membrane. Coupled with Navier--Stokes equation, the aeroelasticequation was solved with time-marching methods, and the aerodynamiccharacteristics of NACA 63-212 airfoil with the inflatable leading edge(ILE) were obtained. From the results, the ILE technique has been applied tosignificantly increase the stall angle of attack and lift coefficient.The values of stall angle of attack and maximum lift coefficient wereenhanced to be 30 percent and 22 percent, respectively. In addition, thedeformation of ILE greatly influenced the flow around the airfoil while theelastic coefficient of material was low. The inflatable structure near thesuck peak deformed clearly, and this hump could induce the separation inadvance.