The dynamic aeroelastic behavior of a trapezoidal wing using a newly formulated 3D enhanced piston theory(EPT) is studied in this paper. The structural equation is built from von Kármán’s large deformation theory and 3D aerodynamic EPT is derived from the convected wave equation, expressed as a power series expansion in terms of inverse Mach number. Special case of 3D EPT satisfy the classical piston theory formulation. The Jacobian transformation along, with Rayleigh-Ritz approach has been used to convert the equations for a cantilevered, trapezoidal plate structure into a cantilevered, square plate structure to solve for the nonlinear oscillation of a fluttering plate through numerical integration. Several cases are studied by changing the sweep angle of the trapezoidal plate for flutter calculation at different Mach numbers from low to high supersonic free stream conditions. © 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.