Abstract: For a class of uncertain nonlinear systems with actuator faults, the problems of actuator fault and unknown disturbance simultaneous reconstruction are discussed. Firstly, a kind of equivalent transformation method for state and output of original system is introduced, and then a reduced-order observer which can eliminate the influences of actuator fault and unknown disturbance directly is developed to get the asymptotical convergence estimation of original system states. A method to reconstruct unknown information is proposed based on the reduced-order observer. Secondly, the estimated derivatives of system outputs are obtained based on the super-twisting algorithm, and the purpose of simultaneous reconstruction for actuator faults and unknown disturbances is reached. Finally, a numerical simulation example is given to show the effectiveness of the proposed methods.