The conventional dynamic surface of Backstepping control is designed as first order filter.Its drawbacks include slow converging speed of tracking/controlling error when closing to equilibrium point, infinite convergence time and vulnerability of the controller gain.In view of these problems, this paper proposes a novel fixed-time convergent Backstepping control scheme based on fixed-time convergent dynamic surface for higher-order multi-input-multi-output nonlinear systems with uncertainties and external disturbance.Firstly, a new fixed-time convergent Lyapunov theorem is proposed and proved.Based on this new tool, the virtual controller and filter of the subsystem of each level are designed with the fixed-time convergent structure.Compared with conventional schemes, the new scheme has the following advantages:1) Speeding up the convergence of tracking error at two stages of far from and closing to the equilibrium point, i.e., the convergence speed is improved within the whole universe;2) Overcoming the parameter vulnerability problem;3) Both the tracking error and controlling error are fixed-time convergent, which means that the convergent time is limited and a fixed upper-bound is existed no matter how big the initial error is;and 4) Both the virtual controller and the controller are nonsingular.