For the nonlinear dynamic model of BTT missile with parametric uncertainties and unknown external disturbance, this paper presented a design method of sliding mode controller based on extend state observer (ESO). The parametric uncertainties and unknown external disturbance was treated as a composition disturbance and ESO was used to estimate unknown composite disturbance and compensated online. The closed-loop stability of the observer-controller combination was proved by Lyapunov method. The controller algorithm is simple, small amount of calculation, and it’s easier for practical engineering application. Simulation results show that the designed controller for the system of missile with the composite disturbance has good robustness and stability. It meets the requirements on the missile fast attitude maneuver and high stability. The performance indices are much superior to those of sliding-mode controller.