An efficient and cost effective procedure, Transonic Equivalent Strip(TES) method has been implemented for unsteady flow computations and applied to transonic flutter analysis. TES method consists of two consecutive correction csteps to a given 2D unsteady code. The first correction step is the mean- flow correction that involves an equivalent airfoil design procedure and the second is the spanwise phase correction which accounts for the spanwise 3D effect. Based on 2D Euler code, transonic flutter analyses have been performed for a rectangular wing with an aspect ratio of 5 and an isolated 45-deg swept-back wing. The present flutter results are in a reasonable agreement with experiment and CFL3D results for a swept-back wing, and LTRAN3 results for a rectangular wing. TES method gives considerable savings in computation time compared with full 3D Euler code.