Abstract: In the scope of application of the United Nations Convention on Contracts for the International Sale of Goods, when the seller delivers the non-conforming goods, the core of the objective criteria for determining whether it constitutes a fundamental breach is that the breach actually deprives the non-defaulting party of what he is entitled to expect under the contract, and makes the purpose of the contract impossible to achieve. In the Guidance Case No. 107, ThyssenKrupp case, the Supreme People's Court concluded that as long as the buyer can use or resell the goods (even at a discount) without unreasonable trouble, the delivery of non-conforming goods does not constitute a fundamental breach of contract, but only a non-fundamental breach of contract. This judgment provides a reference standard for the determination of fundamental breach of contract when the seller delivers non-conforming goods, and the objective standard of CISG fundamental breach of contract is concretized in judicial practice, the success of resale is also an important judgment factor. Balancing of Interest Theory is of great significance to the purposive limiting methods of CISG Article 25 legal interpretation, the case judgment of law application and the determination of specific damages.