Keep at hover an aerial vehicle is one of the most important task to realize when working on UAVs. Once this task is solved, the user can easily give high-orders to move the vehicle. In this paper, a nonlinear super-twisting algorithm to stabilize the nonlinear attitude of a quadcopter is presented. The controller is based on the Singular Optimal Control (SOC) and the Lyapunov theory with the sliding mode technique. Its robustness with respect nonlinear and unknown uncertainties is demonstrated in the stability analysis. Simulations results are carried out to illustrate the well performance of the controllers in closed-loop system even in presence of this kind of disturbances. Main graphs corroborate this fact.