Abstract: A state feedback controller is designed for a class of singularly perturbed systems, where the fast systems are linear but the slow ones are partially input/out put linearizable. Based on the double time scale theory in singular perturbation, an original system is divided into fast and slow subsystems and the latter are in the standard form of affine nonlinear system. The relevant Lyapunov functions are deduced for the linear part and zero dynamics of slow subsystem and the boundary layer system. As a result, the sufficient conditions for asymptotical stability of the system are given through calculating the derivatives of the composite Lyapunov function along original trajectory, then the upper bound expression of Ε singular perturbation parameter is given. Simulation results show the effectiveness and feasibility of the theoretical method proposed.