Banking industry due to its service-based nature is one of the special industries where long term relationship with customers affects its profitability. Encouraging customers and providing special services for them to increase loyalty and refraining from customer attraction by competitors are of main marketing strategies in banking services. Quality of banking services provided for customers plays a major role in increasing their loyalty level, but customers satisfaction with their relationship with bank is more important than quality of services. Development of mutual trust between banks and customers is another factor which affects developing and increasing customers' loyalty. Arrival of new competitors to the area of financial services like insurance companies and mobile network operators indicates increasing importance of banks' movement towards implementation of loyalty programs. This study aims to explore and access to a deep understanding of role and importance of loyalty in banking services system. This study is a qualitative research in terms of nature of data. This study is a descriptive survey in which findings of different researchers have been used. In this study, it is stated that how customer loyalty in banking system affects profitability of banks, and how the banks can increase loyalty of their customers.