An active disturbance rejection backstepping control(ADRBC) approach is proposed for a class of nonaffine systems with dynamical and external uncertainties subject to asymmetrical input saturation. Firstly, by extracting linear control items directly from the nonaffine terms, the nonaffine system is transformed into an affine nonlinear form based on the ADRC ideal. Then during every step of backstepping controller design, an extended state observer is introduced to estimate the total uncertainty of the system, and a tracking differentiator is used to solve the ‘computer explosion’ problem of virtual derivatives. Finally, a novel auxiliary system is designed utilizing hyperbolic tangent function to compensate the control variable deviation caused by input saturation when designing the real control law. According to the Lyapunov stability theorem, it is proved that all signals in the closed-loop system are bounded, and the tracking error can asymptotically converge to an arbitrarily small region of the origin. Numerical simulation results show the effectiveness and a certain engineering application value of the proposed approach.