Abstract: The patent exhaustion principle is to balance the interests of patentee and the public. The defendant in the Monsanto case of USA Supreme Court took patent exhaustion principle as a defense, but he did not succeed. Because of the self reproduction characteristics of seed, there is a conflict between patent exhaustion principle and the patent right itself in the seed field, so patent exhaustion principle should be restricted in this field. Specifically, the patentee can limit the way by which the licensee and purchaser use the patented technology, but this still should be subject to the regulation of patent abuse principle and antitrust law. Although the new plant variety protection system stipulates the exception of the rights of farmers, the rights of farmers will no longer exist if there is also a plant patent at the same time.