Apportionment rule refers to the rule that the value attributable to patent features is recognized and apportioned in the overall value of products when calculating patent infringement damages. This is an unavoidable problem to improve the accuracy and rationality of the calculation of damages. With the development of technology, products are more and more complex and multi-patent and multi-part products are emerging, and thus it is of practical significance and urgency to study the apportionment rule. 

Although the "Patent Law" (Draft for comment) published on January 4, 2019 has further improved China's patent infringement compensation system from the perspective of improving the legal compensation amount and adding punitive compensation system, it still ignores the treatment of the accuracy of the calculation of the compensation amount. In fact, the substantive issue of patent infringement compensation is not the low amount of compensation, but whether the amount of compensation is appropriate. Therefore, it is of theoretical and practical significance to study the accuracy of the calculation of damages for patent infringement, and the apportionment rule is an unavoidable problem to improve the accuracy of the calculation of damages. 

As for the connotation and application necessity of the apportionment rules, the author believes that the apportionment rules have the system rationality, and the correct application of the apportionment rules will not reduce the patent value, and the quantification difficulty will not constitute the substantive obstacle to its application. Under the international background that the apportionment rules have been widely recognized by the judicial practice of the United States and Japan, it is necessary to consider the application of the apportionment rules when calculating the amount of patent infringement damages. 

The author further studies the legal basis and judicial cases of apportionment rules in China. It is found that there are many problems in the application of apportionment rules in China, mainly reflected in two aspects: the scope of application is unclear and the application mode is not standardized and specific. Based on the comparative analysis between China and the United States, the author believes that, on the premise of meeting the applicable conditions, the apportionment rules should be applied in judicial practice in China, whether it is the way of "lost profits", "infringement profits" or "reasonable royalties". In view of the application of the apportionment rules, the author believes that it is necessary to add the limitation of the overall market value rules when regulating the apportionment rules; As for the situation of the infringement of parts or packaging, the situation of the other value contribution of the infringer to the infringing products, and the situation that the infringing products cover multiple patents at the same time, the apportionment rule should be applied; the methods to determine the apportionment ratio from the best to the worst are: alternative comparison method, consumer investigation method, quantitative proportion method and qualitative analysis method. At present, there are only cases that apply the latter two methods in China, which should be continuously studied and improved; the burden of proof of apportionment rules should be borne by the infringer, which is more in line with the current judicial policy and the application status of apportionment rules.