A new dynamic saturation function is developed for a class of strong coupling and nonlinear system according to the definition of approaching angle. Approaching ability is proved by continuous approximation of the dynamic saturation function. Then fast terminal sliding-mode hyperplane is advanced based on the function. Arriving process is assured

chattering and singularity caused by parameters is eliminated more effectively than switching hyperplane designed without dynamic saturation function. The robust tracking control law with the function is approved based on Lyapunov stability theory and finite time convergence is further verified. Finally

effective dynamic equations are developed under different flight conditions of variable structure near space vehicle. Application of above control method in flight control system is achieved by designing control hyperplanes and laws of fast and slow channels respectively. This new method compensates the disadvantages due to parameter uncertainty and outside disturbance. Simulation demonstrates the rationality and robustness.