Abstract: With the improvement of the intellectual property protection environment and the enhancement of entities’ capacity in using the intellectual property system, the number of patent litigations in China continues to increase. Accompanying the surge of patent litigation, the issues of slack patent protection, high cost for rights protection as well as low cost of infringement are highlighted. Based on the first-instance data of patent civil litigation from 2000 to 2014, this paper defines the repeated litigated patent from the use of the same patent to initiate two (and above) litigations and eight (and above) litigations, respectively. Focusing on the impact of repeated litigated patents on the probability of winning for the plaintiff, the main conclusions are as followings.First, the improvement of China's intellectual property protection intensity, especially the revision of the damage awards standard in the Patent Law, has pushed up the number of patent litigations and further led to significant growth in repeated litigated patents.Second, although a large number of  design and utility models have been used in patent litigations, there are still invention patents experiencing repeated litigations. Furthermore, the repeated litigated patents appear more in case of invention patent when the year, industry as well as region fixed effects are controlled, which is totally different from the case of overall litigated patents.Third, at present, China's repeated litigated patents mainly occur between domestic entities, and are concentrated in the traditional manufacturing industries. The pharmaceutical, chemical, and semiconductor industries with frequent patent litigation internationally have not produced a large number of repeated litigatedpatents in China. The phenomenon that repeated litigated patents concentrating in software industry and business methods domain in United States are also not obvious in China. Meanwhile, China has not yet been affected by repeated malicious litigations issued by overseas entities.Fourth, compare to the case in the United State in which the plaintiff always lose for the repeated litigated patent trials, the plaintiff with the repeated litigated patent is more likely to win the trial in China, especially for the injunction trial. Possible infringements in the market can be suppressed, but the amount of damages has not been positively correlated with the repeated litigated status. Fifth, the probability of plaintiff’s winning has significant regularity. The invention patent and the handling time have a negative correlation with the plaintiff's winning rate; the more the plaintiff initiated the lawsuit, the plaintiff is the enterprise, and the defendant is the non-enterprise, the plaintiff has a relatively higher winning rate. In addition, affected by the forum shopping effects, the plaintiff’s winning rate is also closely related to the choice of the trial court.This paper holds that the phenomena of repeated litigated patents are likely to be the strategic commercial behavior of domestic innovative companies to protect their own market, via targeting at retailers (or batch counterfeiters). On the one hand, it is related to collective infringement and repeated infringement in the production and sales sections in the traditional manufacturing industry in China. On the other hand, it also reflects the inefficiency in the judicial litigation system caused by repeated litigated patents. A well-functioning system design relies on high-quality patent output, a complete patent objection and infringement monitoring system, and a judicial compensation amount that can generate sufficient deterrent effect. Among them, the high patent quality raises the threshold for infringers to imitate patented technology, the high litigation costs and high compensation amounts can deter potential infringements, while also preventing unrestricted patent litigation. However, the repeated litigated patent litigations have undermined the formation of these mechanisms.The high-sue rate cases for the same patent frequently initiated in the Chinese patent civil litigation field indicate that the dispute itself is not ambiguous, and even no special procedures, techniques and knowledge are needed to judge the fault and breach of contract liability. In theory, the plaintiff will resort to the court only if he or she has a greater degree of confidence in his or her victory; when there is insufficient confidence in the judicial process, or the execution cost is too high, the plaintiff often does not resort to the court, and thus forms the adverse selection in the process of judicial case trial. When the adverse selection effect occurs, the plaintiff in some dispute cases may lose the trust for the national judicial system, and further promotes the strategic “knock-and-roll” behavior (the local strategic litigation behavior in China shows the feature of lower requirements for damages and using low-quality patents to exercise blackmail). Undoubtedly, this will also cause manufacturing companies to be affected by infringement charging, which in turn affects normal production and operation activities.Based on those empirical evidences, this paper proposes to strengthen the investigation and analysis of repeated litigation behaviors, and prevent a large number of repeated litigated patent cases, especially low-quality patent cases from flooding into the national judicial system, and formulating effective countermeasures. The first is to establish a unified handling mechanism for repeated litigated patent cases, improve the efficiency of handling similar cases, improve the trial jurisdiction system of professional intellectual property courts, and enhance the consistency of trial results. The second is to strengthen the effective connection between judicial and administrative patent enforcement, avoid the emergence of judicial adverse selection, actively adopt administrative means to effectively combat repeated infringement and malicious infringement, and steadily improve the actual amount of damages. The third is to vigorously cultivate professional market rights protection institutions, improve the arbitration mediation system, and build a four-in-one intellectual property dispute resolution mechanism including the judiciary, government, market as well as society, and create an institutional environment and market environment that is more comprehensive and more conducive to promote innovation.

Key words: patent litigation, patent infringement, patent court, repeated infringement, damage awards