Reputation system play important role in securing today’s communication systems. Online reputation system gaining popularity as dealing with malicious ratings in reputation systems has been recognized as an important but difficult task. This problem is challenging when the number of true user’s ratings is relatively small and unfair ratings plays majority in rated values. In this paper, we propose a new method to find malicious users in online reputation systems using User Behavior Analysis and Quality Repository Approach(QRA). We mainly concentrated on abnormals detection in both rating-values and the malicious users. Proposed method is very efficient to detect malicious user ratings and aggregate true ratings. The proposed reputation system is evaluated through simulations, proposed reputation system can significantly reduce the impact of unfair ratings and improve trust on reputation score.