A new characterization of control Lyapunov functions is presented for non-linear systems with structural uncertainty. Based on this characterization, we deal with the problem of globally asymptotical stabilization of two classes of non-linear systems with structural uncertainty. Sufficient conditions for the globally asymptotical stabilization of the closed-loop system are acquired respectively. In addition, state feedback control laws are designed respectively to globally asymptotically stabilize the equilibrium of the closed-loop system. Finally, the simulations show the effectiveness of the method.