In this paper,a constrained adaptive control approach is proposed for nonlinear system with unmatched uncertainties.Fuzzy disturbance observer is used to approximate the unknown and unmatched uncertainties online.The backstepping method is adopted to design the adaptive controller.The command filter is introduced into the control system,which can effectively decrease the effect of the control input saturation on system stability.The controller design avoids the repeated derivation for the virtual control law.The closed-loop system is verified to be asymptotical with Lyapunov stability theorem.Simulation results show the effectiveness of the proposed method.