Abstract: In chemical,oil refinery and power industries there are many chain energy systems.Socalled chain energy system is made up of some unitary devices chained up,and each unit is allowed to exchange energy or mass with the outside of the system.Applying the idea of thermoeconomic isolation,a new method of thermoeconomic isolation on the chain energy systems is presented,and its convergence is proved meanwhile.It is the essene of the method to achieve thermoeconomic isolation on chain energy systems that two known parameters located at the start unit and the end unit are used to adjust and determine the unknown maginal exergy cost of each unit by the way of press and squeeze,and make them converge on correct result.An example of applying the method to a nonlinear chain energy system shows that the method is effective. The method will help to break a new path to make thermoeconomic isolation be achieved in other types of energy system.