Abstract: In this paper, the controllable well-posed problem of the completely controllable matrix pair (A, B) is presented and studied. When B has the economical control structure, the above problem becomes the controllable well-posed problem of the synthesis solution of economical control structure. The well-posed problem in MES synthesis of linear control system discussed in the paper 1 is a special case of the problem investigated in this paper. By perturbation theory of eigenvalues two methods for analysing the above problem are given, and the bounds of perturbation of the relevant elements in the matrices are given.