Abstract: Following the two synthesis methods, the search and the fixed mode method, of economical information structure (EIS) for stabilization and pole assignment of the system, a third synthesis method, the decomposite-composite method is presented in this paper. The third method, by which the above mentioned EIS can be obtained, not only is simple, but also brings to light the relation between the replaced eigenvalues and the distribution of information channels in EIS. The fixed mode method is complementarily introduced. Besides, the decomposite-composite method is demonstrated in detail. Some examples are given for illustration.