The growing and diverse applications of low Reynolds number operating vehicles impose the need for their accurate study. Optimization is an important part of computational science that can improve the performance and increase the efficiency of the initial geometry. most of the research studies on aerodynamic optimization were focused on high Reynolds number airfoils. But for aerodynamic devices that have small dimensions, like MAVs, usually the flow speed is low and thus the unsteady effects caused by boundary layer separation cannot be neglected. In this article, oscillating airfoil with pitching motion in turbulent and low Reynolds flow has been optimized with the continuous adjoint method. Drag to lift ratio was chosen to be the objective function and free form deformation parameters is adopted for the surface geometry perturbations. Since aerodynamic optimization generally consists of two parts, first solving the flow equation and then computing the gradient of the objective function, in this article in order to evaluate the accuracy of the optimization process both has been validated. The results show that the adjoint equation converges well and with specifying the suitable constraints, the designed shape approaches to the most optimized level without the loss of performance.