Sending demand letter of patent infringement is a common way for patentees to enforce their rights,and it may also become a means for some patentees to seek illegal benefits.The "Libang case" and "Shuanghuan case" trialed by the Supreme People's Court reflect that China's standard supply of patent demand letters is insufficient,and the judgments of judicial organs are inconsistent.This is not conducive to the reasonable distinction between enforcing rights and abusing rights.According to the theory of right types,combined with the US legislation governing "patent trolls" abuse demand letter and the judicial practice of applying the Noerr-Pennington Doctrine,the demand letter is in nature the second right of the patentee,namely the right of remedy or the right of petition.It is not an act of exclusive right to exercise,let alone an offer.It has the effect of saving the cost of enforcing rights,improving the efficiency of dispute resolution and reducing the judicial burden.Sending demand letter should abide by the boundaries of rights,and must not abuse rights or engage in unfair competition.China should specify the subject,object,content,evidence and form requirements of the demand letter in the patent law under the path that rights cannot be abused,as the basis for sending demand letter and judging its legitimacy.The subject of sending demand letter is limited to the patentee,the exclusive licensor the sole licensor (when the patentee does not exercise the rights),and the legal heirs of the patentee.The target of the letter is limited to those who illegally exploit the patent,including manufacturer,user,who offering for sale,seller or importer.The content of the letter should include the name of the patentee,the address of the patentee,the warning items,the name of the patent,the patent number,the validity of the patent,and the specific facts that the alleged infringing product,service,or technology infringes the specific claims of the patent.Warnings include stopping infringement,paying license fees,or compensating for losses.The evidence in the letter should include evidence of ownership,evidence of infringement,and evidence of loss (if compensation is required).The letter should be in written form,including letters,faxes,and e-mails,but not news media.The patent law should also stipulate the criteria for judging the abuse of demand letter from both objective and subjective aspects,that is,the demand letter is objectively false as the first element,and subjective intentional or gross negligence is the second element.The so-called objective falsehood includes:(1) the claimed patent is invalid;(2) the person being warned does not infringe any claims of the claimed patent;(3) the sender is not the patentee or subjects with independent remedies.The behavior of subjective intention or gross negligence is manifested as:(1) failure to inspect the recipient's products before claiming infringement;(2) failure to seek expert advice or opinions before claiming infringement;(3) failure to claim infringement to the producer before claiming infringement;(4) knowing that the patent is invalid before claiming infringement;(5) falsely claiming that one has patent rights;(6) other deliberate,extremely negligent or credulous acts.Unless the above two requirements are met,the sender shall not be liable for tort.