Aiming at strict-feedback nonlinear systems subject to external mismatched disturbances,the fixed-time control problem is studied.Based on backstepping control strategy and Lyapunov stability theory,the design steps of a novel disturbance observer and controller are given,which can realize global fixed-time stability.The traditional fixed-time backstepping control algorithms often suffer from singular problems caused by repeated differential operation of the virtual control laws.To address this problem,a smooth backstepping controller is designed without using the fractional power items.The disturbance estimation is compensated into the nominal controller in the design,which realizes high-precision,fixed-time stability of control object under external disturbance,and guarantees that the signals in the closed-loop system can converge to stability within fixed time.Finally,the effectiveness of the proposed control scheme is verified through comparative simulations.