This paper tries to develop a mathematical model to assign an optimal site for Insurance Organization branches in eastern part of Tehran by using the data of Social Insurances Organization. So, designing and developing service network and determining a proper site to set up the centers of services is a vital issue. Factors affecting the location include land price, ensured population, closeness to the parking, organizations, clinics, banks, underground-station, bus-station, highways. By using questionnaire and performing pair-wise comparisons of the determinants and then analyzing the data collected by Eigenvector method, the effectiveness coefficients of each determinant will be determined. Numerical results of MADM model will be inserted in the second objective function defined as 0 and 1 that means the organization branch in that location must set up or not. Finally, the model will be solved by Excel and a proper location determined for setting up the branches.