Aiming at the attitude tracking control problem of quad-rotor UAV under input constraints, a parametric control method is proposed.Firstly, a second-order, full-actuated model of quad-rotor attitude error is established, and a parametric controller is adopted to make the attitude error system equivalent to a first-order steady closed-loop system, which make the attitude errors converge to the tracking signal.Considering the input constraints and for better tracking performance of the quad-rotor, an intelligent optimization method is adopted and the particle swarm optimization algorithm is used to optimize the parameter matrix in the control law.The simulation experiment shows that compared with the backstepping method, the proposed parametric controller can track faster the attitude commands with input constraints, which has better transient performance, thus can realize high-precision attitude tracking of the quad-rotor UAVs.