The problem of disturbance decoupling with stability is investigated for a class of single-input single-output(SISO) nonlinear systems, in which the states are not available for feedback. A novel fuzzy adaptive high-gain observer is firstly designed to estimate the unmeasured states. Then, by combining adaptive fuzzy backstepping design and small-gain theorem with supplying function, an output feedback control design is described to achieve the asymptotic stability of the closed-loop system in the sense of input-to-state practically stability(ISpS) with respect to the disturbance input, while the effect of the disturbance on output is diminished to an arbitrary degree of accuracy. Simulation results show the effectiveness of the proposed approach.