The longitudinal equations of motion for a flexible launch vehicle controlled by ffirust vectoring are derived and optimal attitude controller of the vehicle is designed. When the engine inertia effect is included in the equations of motion, additional Tail-Wags-Dog TWD zeros are produced in the launch vehicle system. As the TWD zeros related with the high-order structural bending mode affect the stability of the flexible launch vefficle, this effect should be considered in designing the attitude controller. The attitude control system of the flexible launch vehicle composed of the classical type controllers are optin-dzed by the Evolution Strategy (ES), which is a stochastic optimization technique. Optimal attitude controllers are designed for the engine inertia effects and the design results are analyzed.