The number of bank mergers in 1990s has increased 215%. (Becher, D.A., 1999) From 1987 to 1997, the value of mergers and acquisitions in the world financial industry has reached nearly 1.4 trillions of US dollars. (Cybo-Ottone, MurgiaSince, 2000) Since bank mergers become popular, there has a controversy about whether bank acquisitions create value for target and bidder shareholders. This paper gives a literature review about this paradox and it is divided by four parts. First part is the reasons for bank mergers. Second part shows the literatures before 1990.