To address the trajectory tracking control challenges of parafoil systems in complex high-altitude wind fields, a sliding mode control method based on a fixed-time observer is proposed. The dynamic model of the parafoil system based on added mass is established by analyzing its basic structures and parameters. To improve the trajectory tracking control accuracy under nonlinear, strongly coupled characteristics, and unavoidable uncertain disturbances during flight, a trajectory tracking sliding mode controller is designed. A saturation function is employed to replace the traditional sign function to suppress the chattering problem of sliding mode control. For wind field disturbances, a fixed-time disturbance observer is designed, and the estimated wind disturbance values are used to generate additional control signals integrated into the sliding mode control law, enhancing the disturbance rejection capability and robustness of the controller. Simulation results demonstrate that, compared with conventional PID controllers, the proposed trajectory tracking controller significantly reduces tracking deviations, achieves higher landing accuracy for the parafoil system, and effectively suppresses the adverse effects of external disturbances, exhibiting superior robustness and anti-interference performance.