In this paper, we consider a dynamics assignment problem in decentralized servomechanism. The dynamics assignment problem is defined as the problem to assign the dynamics in the reference input. With this assignment, the dynamics of each local controller based on the assignment results are simpler than that based on the original reference input. In this dynamics assignment problem, a criterion based on the total energy of the local controllers among the subsystems is defined and analysed. MiniMax Principle is applied in the paper to do the assignment according to the criteria. The calculations for each assignment result with MiniMax Principle are compared to those by exhaustive search in an example. Monte Carlo experiments are also conducted in the end to illustrate the comparative effectiveness of MiniMax Principle in this dynamics assignment problem.