Destabilizing effect of magnetic damping on the supersonic panel flutter is investigated. The linear piston theory is available to formulate the air force at high Mach numbers. A plate in supersonic flow can be stabilized by reducing the compression force perpendicular to the flow. However, once the dynamic pressure parameter exceeds some critical value, the time rate of motion becomes complex then the flutter occurs. In this paper, the strength of in-plane magnetic field to reduce the panel flutter under higher dynamic pressure parameter is determined. Due to the complexity in finding the exact solution of plate motion, Galerkin solution with different terms of truncation is adopted herein. Therefore, the exact solution can be obtained by using the four-term solution as an initial value. The most attractive feature is that the supersonic flutter can be avoided efficiently through the application of in-plane magnetic field.