Competition of Taiwan banking market is severe. Relationship marketing plays an important role for Bank's competence. The customer satisfaction towards the bank products or service just a starting point in the building of long-term relationship with the banks. The major factors that determine the success of the relationship marketing are the customer loyalty. However, the central issue is how to transfer the customer satisfaction to the loyalty. Through the literature review on customer relationships, we realized the psychological and physical factors of the commitment behind customer loyalty might play the mediating role. A conceptual model is established that the commitment transfers the customer satisfaction to the loyalty. In this model, the components of customer satisfaction-service quality and attractiveness of alternatives influence loyalty are tested to influence the components of commitments—affective and continuance commitments respectively. Then an empirical research among 317 bank customers of Taiwan was conducted to test the conceptual model. The results are gathered from a street interview-survey in the central cities of Taiwan, and show that commitment is a crucial mediator in nurturing customer loyalty from the satisfied customers. Since promoting customer loyalty is a paramount issue for banks, this paper is believed to make a marginal contribution for Taiwan Banks.