Due to extension of human life consumer, groundwater resources in recent decades have been increasingly intruded by contaminants. Nowadays, the great challenges facing engineers and experts are groundwater protection against contamination inputs and reduction of specific pollutants of these resources. Therefore, monitoring and evaluation of aquifer with a view to quantity and quality can play a significant role for preservation and management of water resources. The Sia-Mansoor aquifer that is located between Dez and Galal –e-Konak Rivers in the east of Dezful city is one such area where looked to be susceptible to pollution. With attention to industry, agriculture and biologic pollutants in the area, the Sia-Mansor aquifer was evaluated to identify its probable contamination. Therefore, 16 samples from drinking and agricultural wells and 6 samples from surface waters in wet and dry seasons were collected. The concentration of major ions (Ca+2, Mg+2, Na+, HCO3 , SO4-2 and Cl-), were measured and total coli form, fecal coli form and bacteria such as salmonella paratyphoid, shigella dysenteries, proteus valgaris, campylobacter jejuni, staphylococcus aureus, staphylococcus epidermis, entrobacter, citrobacter, E.coli, rota and entero virus were also detected. The results indicated that in adjacent to Ajirob stream (west of the area) quality of groundwater is better with respect to other parts and at present the area is not facing nitrate problem. But the outcome of investigation has depicted intensive bacteria contamination of the area and at least in each sampling station one bacterial contamination was found. The main factors for aquifer contamination include: 1) vicinity of exploitation wells to toilet wells, 2) villages swage output and 3) animal manure. It is to be noted that high vulnerability potential of the aqufer facilitates contamination problem.