Abstract: The identification problem of the impulse response of a continous plant in closed loop control system is investigated via block-pulse function approach. An algorithm is then dervived for the piecewise constant solution of the plant impulse reponse, based on the known dynamics of the controller and the feedback component and the given reference input and system output records. Since the algori thm is in sequential form, the operation for matrix inversion can be avoided, and conseque-ntly, the computational effort may be saved greatly.