Abstract: It is presented in this paper a Modified Interaction Prediction Method,which can be used for dealing with the hierarchical optimal control problem of certain large scale systems in which there exist not only state interconnections but also control variable interconnections between subsystems.And also an application of this method to a distillation column is given.The results of computer simulation show that almost the same result can be obtained by both the Modified Interaction Prediction Method and the Global Optimal Control Method.