In this paper,the authors deem that the retailer's competitive advantage derives from retail business process,while the characteristics of business process come from the retailer's resources.On the basis of that,we build up a research model of the forming mechanism of retailer's competitive advantage,and do a case study on Wal-Mart according to this model.The competitive advantage of Wal-Mart is that "Everyday is low Price",which comes from business process of "low cost purchasing-low cost delivering-low price selling-low cost purchasing".The guarantee of Wal-Mart's business process lies in the enterprise's resources that include logistics system and information system, as well as the family relationship with the customers and the partner fellowship with the employee.