The paper researches smooth switching controller for multi linear time-varying (LTV) systems with input quantization and input saturation, which is a common problem for modern flight vehicles. First, this paper presents the problem statement, in which a tracking problem is converted to a regulation problem by constructing deviation system, the tracking error is treated as the system performance and the conditions for smooth switching tracking control are discussed based on the theory of robust control technique. Secondly, controller of the deviation system with input saturation and input quantization is designed by solving Linear Matrix Inequalities (LMIs) based convex optimization problem with the conditions for smooth switching tracking control being considered. Finally, simulations are carried out for the longitudinal dynamics model of hypersonic reentry vehicle (HRV) driven by Reaction Control System (RCS) to illustrate the effectiveness and rationality of the method.