Attitude stabilization for complex nonlinear spacecraft with flexible appendages is researched at the presence of external disturbances and orbital maneuver. A flexible spacecraft attitude controller based on sliding mode algorithm is proposed, which only needs the information of attitude angular without the knowledge of the attitude angular velocity and exhibit excellent robust performance. The paper demonstrates the close loop system stability employing the Lyapunov stability theory. The simulation results illustrate this flexible spacecraft attitude control system maintain stable in spite of external disturbance and orbit control force.