Frontline employees are an important source of differentiation and competitive advantage in the service sector. So in banks as the most important economical and service sector enterprise, employees organizational citizenship behavior is very important. Because Such employees are the most important source of competitive advantage. The purpose of this research studying soft factors that correspond to behavioral area and create competitive advantage in organizations and does organizational citizenship behavior cause competitive advantage, at last a comparative study about the situation of those factors in Tejarat and Mellat banks have done.
   This study is a quantitative study that is done in1390- 1391 in a sample of 1100 employees and customers of 76 branches of Tejarat Bank and 73 branches of Mellat Bank. To gather data two questionnaires for employees and customers based on Likert Scale are used and they are analyzed by descriptive and inferential statistics methods. To determine the constructs of the conceptual model variables PLS software and structural model are used. Composite reliability and Cronbach Alpha are used to measure questionnaires reliability, so all of the factors coefficients are more than 0.7. Discriminant validity  by Average Variance Extracted (AVE) indicator is used to determine convergent validity, so the  AVE indicator is more than 0.5.  Discriminant validity in the research constructs has good fitness. So the average variance square root is more than the correlation coefficient between each concept and the concepts. Findings show that the model has good comeliness totally and all the parts of the model including measurable parts and structural parts are meaning full. So the individual, managerial and organizational factors create organizational citizenship behavior and these factors create competitive advantage by organizational citizenship behavior. It is also found that the banks should promote organizational factors including organizational support, organizational justice and organizational culture  and draw up suitable strategies and long term plans. This kind of studies can be used by managers to increase human resource and organization productivity