Abstarct: Wastewater treatment along with preserving the environment in urban and industrial areas, will result in the reuse, recovery and recycling of the disposed water. One of the requirements for appropriate recycling of the urban sewage is the correct selection of the location for the wastewater treatment plant with regard to the effective parameters. In this thesis, using the various parameters lithology, vegetation, land use, soil specification, topography (slope), elevation variance of city, distance from the urban area as well as the highways and rural roads, power transmission lines, primary rivers, urban and rural areas, water wells, Qanats and aqueduct, border of roads and fault, the appropriate location for construction of wastewater treatment plant of Flawaerjan city is introduced. Site selection was performed in two phases. In the first phase, analytical hierarchy process method was integrated to GIS to determine the suitable arenas. In the second phase, baxsed on of the field survey and the techniques of similarity to ideal solution method (TOPSIS) the selected area in the first phases were ranked. Then baxsed on the environmental impact assessment, the most appropriate site for construction of wastewater treatment plant was proposed. The most suitable site is located in 12 km, southwest of Falavarjan city.