In modern organizations, knowledge is the fundamental basis of competition. In the new context, two major factors determine the future survival or success of organizations: electronic commerce and the knowledge from customers. Thus, the goals of the research were figured out, and investigating the relationship and application of customer's knowledge management in gaining competitive advantages of organizations in E-commerce and also the 8 followings factors were investigated: knowledge from customers, knowledge for the customers, knowledge about customers, recording and spreading customers' knowledge, quality of the products and services, pace of providing the products and services, reasonable prices and satisfaction as the output and result of using customers' knowledge management on organizations competitive advantage variable in Ecommerce. For the statistic society, people who were all experts and elites of Mellat Bank market development organization were chosen, and 210 experts who are working in Iranian insurance companies. The statistic tests used were: Kolmogorov-Smirnov, simple linear and multiple regression the results extracted from the above tests stated the linear relationship and correlation between independent and dependent variables. The results of this study had shown the application of the customers' knowledge management would lead into gaining competitive advantage for the organizations in E-commerce. [ABSTRACT FROM AUTHOR]