The tracking control of chaotic Chen system is realized using a nonlinear single-input controller. According to the structure characteristic of the Chen system, proper feedback form is selected and an adaptive single-input controller is designed, which makes the Chen system track a certain variable of the Rossler system with unknown parameters. The Lyapunov direct method is applied to prove that the error signal asymptotically approaches zero. Numerical simulations show that the proposed control method is feasible, and the identification of unknown parameters can be realized.