In light of the situation where an invention asserted in multiple suits against infringers in different countries happened more frequently, the doctrine of issue preclusion had become increasingly important to patent litigants. However, claim preclusion cannot provide resolution to it because the parties and accused products may not be the same between the first and second judicial proceedings, despite of the same invention at issue. Instead, we need to establish the issue preclusion mechanism to our patent system to acquire efficiency, while avoiding inconsistent judgments. After comparing with the U.S. system, this article suggests that, in order to establish issue preclusion based on the foreign patent judgment and prosecution history, our patent system is currently in want of reform. In particular, there are three kinds of regulations to which we must conduct reform, i.e., preclusion regulations, patent regulations, and evidence regulations. Although Professor Louch had introduced the concept of issue preclusion into our country decades ago, the statutes as a whole have not been properly constructed to serve as a functioning platform in this regard. Ironically, associated statutes are preceded by courts’ issue preclusion decisions rendered to certain cases, a judge-made law phenomenon which does not traditionally appear in a civil law country due to lack of the stare decisis mechanism. We hereby must manage to amend the current statutes to lay out a proper foundation for providing issue preclusion effect needed. To be effectively applying issue preclusion, it is necessary to ensure the satisfaction of the “identical issue” requirement which turns out to be the most complicated one among the four factors test initiated by In re Freeman due to the variances of regulations among countries. Therefore, we need to harmonize our patent regulations with the rest of the world. While file history itself is intrinsic evidence, however it becomes extrinsic evidence when containing a statement made to foreign counsel or patent office examiner. We need to amend the regulations of evidence classification, and even provide a heighten-of-standard-of-proof mechanism to deal with extrinsic evidence such as file history.