The principle of changed circumstances has been defined in the Civil Code of PRC with the view to fitting the complex requirements and constant development of society,maintaining the order and justice of society,which is an amendment to the theory of“contract must be kept”in original contract performance.The changed circumstances is significant when the party suffers obvious unfairness for continuance of performance in a contract which is not caused by force majeure or commercial risk.Some problems,such as specifying an identification standar...