A method using the concept of equivalent stiffness was developed for the modal and flutter analysis in wing preliminary design. The stiffness matrices calculated from different stringer-stiffened panels were applied to FEM shell properties of the same planform panels (i.e, unstiffened panels) that had the same mechanical properties as those of the origin stringer-stiffened panels. The advantage of the method was that modeling stringers was avoided in the equivalent finite element model (EFEM) and the complicacy of finite element model was reduced, while the feature of structural layout of wing was still retained. A wing of the notional civil jet was used as an example to verify the method. The detailed finite element model (DFEM) and the EFEM of wing were created and analyzed for flutter prediction. The results indicate that the natural frequencies, mode shapes and flutter speed from the two models are in a very good agreement. The accuracy of the EFEM for the modal and flutter analysis of wing is verified. The EFEM provides an attractive method for wing flutter prediction in aircraft preliminary design phase due to its rapid modeling and satisfactory accuracy.