The Rossler system is controlled by an adaptive control method. When the parameters of the chaotic dynamic system are unknown, based on Lyapunov stability theory, appropriate controller and parameter adaptive law are designed. The asymptotic stability of the transformed system at the origin is proved by theoretical derivation, and the conclusion that the original system can be controlled to the unstable equilibrium is proved theoretically. The simulation results of the system show that the system can be controlled to any unstable equilibrium point to achieve the control purpose, which verifies the effectiveness of the method.