Based on Lyapunov-Krasovskii functional, this paper concerns an observer-based stabilization problem for linear time-delay systems with delayed state and input. If the time-delay constants are both availabl for the li.near time-delay system, an observer-based controller, in which the influence of the time-delays is considered, is given. And the design of the controller and observer satisfies the separation principle. If the time-delay constants aren’t precisely known for the linear time-delay system, an observer-based feedback controller with adaptation to delay parameters is first given. Then the adaptive controllers are derived by Riccati matrix inequalities.