Abstract: From the view point of the bicriterion optimization concerning parameter estimation and optimum control, a four-level hierarchical model following controller for a non-linear system is presented by means of decomposition-coordination technique of the large scale system. The algorithm is applied to solve a practical problem of controlling the excitation of the synchronous machine with unknown parameters. Simulation results show that the algorithm is easy in caculation and clear in structure. It not only makes the parameter estimation more accurate but also enables the non-linear plant response to follow that of the linear model quite closely.