In the practice of international sales of goods，it is very common that the seller declares the contract avoided once the buyer breaches the contract.Under the automatic avoidance system，thecontract's effect becomes uncertain after the contract is terminated. To resolve this problem，CISG sets up the system of declaring the contract avoided. But it can'ttotally resolve the problems whether the precondition of terminating a contact is fulfilled by declaring the contract avoided，actually，it often happens that sellers improperly or illegally declare the contractavoided. So，by the method of theoretical research and case studying，this article researches the value of the system of declaring the contract avoided under the CISG，probes into the application of Article 64 in legal practice and also sets forth the relationship between sellers declaring the contract avoided and buyer's remedies forbreachof contract. Furthermore，this article elaborates the value orientation of the system of declaring the contract avoided under CISG and its application rules.