In this paper flutter phenomena for a cropped wing with an external store using numerical and experimental methods in a subsonic and incompressible flight regime has been studied. Wing structure was modeled base on von Karman plate theory. A 3D time domain unsteady vortex lattice method was used for wing aerodynamic model and a slender body aerodynamic theory was used for store aerodynamic model. Finally, the aeroelastic governing equations with considering vibratory wing motion has been solved. The experimental tests were performed in an incompressible subsonic wind tunnel. Comparison of experimental results with theoretical analysis shows good agreement with each other especially in calculation of aeroelastic behavior of the wing. In continue, the effects of some parameters such as wing thickness, wing aspect ratio, store position, weight of the store, aerodynamic of the store, store vertical distance from under wing, and center of mass of the store on both flutter speed and instability boundary of the wing have been studied analytically and experimentally. The results show with both increasing aspect ratio and decreasing wing thickness, flutter speed will be decreased. Moreover, change in store position effects on flutter speed of the wing/store configuration. Aerodynamic of the store has no significant effect on flutter speed of the wing/store configuration and increasing store weight leads to increasing flutter speed. Change in center of mass of the store influences on flutter speed.