This article is study on the reverse payment settlement between patent holders and generic drug manufacturers and how the court evaluated the illegality of these settlements. Under these agreements, a generic manufacturer agree to refrain from entering the market for several years. In return patent holder compensate the generics with payment of monetary or non-monetary benefits. Although aspects of the pharmaceutical settlement system(or the pharmaceutical patent linkage system) create troubling incentives that may promote anticompetitive cooperation, the U.S. supreme court in FTC v. Actavis, Inc, held that these reverse payment settlement are subject to challenge under antitrust laws. Furthermore the court applied the rule-of-reason analysis. In the same manner, the EU Commission has been monitoring patent settlements in order to identify those settlements which could be potentially anticompetitive from an antitrust prospective. Pay for delay agreements those that limit generic entry against a value transfer from a brand-name drug to a generic manufacturer, these agreements violates EU antitrust rules that prohibit anticompetitive agreement. The korean supreme court's decision in GSK v. Donga pharmaceutical Inc. provided an response to the issue that standard on exemption of patent rights activities and evaluation these settlements. According to the decision, even settlements within the patent's exclusionary potential were not automatically presumed lawful and the potential risk to competition is obvious in the reverse payment settlement. Anti-competitve effect of a settlement depends on various factor including the payment's size, scale, patent holder's market power, patent validity. Defendant should be allowed to provide pro-competitve justification while the court conducts a balancing test to decide whether the reverse payment settlement passes antitrust law.