An essential condition for the synthesis of any system consits in its description. Here we only assume the existence of an analytical description of the dynamic system behaviour.Nowdays a sufficient number of different mathematical structures describing the system behaviour is known. Because of the incomplete a priori information adaptive models achieve considerable importance.Basing on continuous observations of the process these models correct and adapt those model-parameters, that determine the state of the model in accordance with varying system conditions. After a brief description on the identification a method for identifying dynamic systems is explained using adaptive models. Advantage of this method is the simple structure of the model and the possibility to adapt the model continuously.