The control law of tracking the prescribed trajectory and the domain of attraction for the fixed-wing unmanned aircraft are investigated based on its longitudinal motion. First, the piecewise-linear system is established to approximate the original nonlinear system by linearing the nonlinear dynamic system along the referred trajectory in the perching process of the aircraft. Second, on this basis, the switching control law of tracking is designes which combined the optimal control theory and the overall stability analysis method of switching system. Third, in order to estimate the domain of attraction and ensure that the aircraft can fall in the target area, the sum-of-squares optimization is presented. Finally, the tracking controller is validated and the domain of attraction is certified correct by simulating fixed-wing aircraft in the perching process.