Determining the relationship between biotic and abiotic factors and their effects on water quality and eutrophication plays important roles in managing and optimizing the efficiency of dams. Therefore, in the present article, the above relations with emphasis on the results of one-way and multivariate statistical analysis were investigated in Sanandaj Azad dam. Monthly Sampling was carried out in 5 stations in 2015-2016. All environmental parameters (Water temp., Secchi disk, Turbidity, pH, DO, DO%, BOD5, COD, EC, NO3-, PO43-, Chl-a) and microbs (Total counts, Total coliform, Fecal coliform and Fecal Streptococcus) were analyzed based on standard methods. (According to the results, low numbers (less than 0. 1 CFU / 100 ml), of streptococcus and fecal coliform in all samples were a good sighn of fine water quality in terms of non-contamination with fecal (resistant and old) and (fresh) microbes. In the step wise linear regression test, the coefficient effect of trophic state, based on chlorophyll-a and transparency depth on the total trophic index was obtained more than the nutrients trophic index. According to the principal component analysis (PCA), the trophic state index and chlorophyll-a concentration (in the first component) were the most important factors on quality of the water. While the water quality index and its parameters (inorganic phosphorus, BOD5 and coliform) were included in the second component. Among the environmental parameters affecting the quality of water, the percentage of saturated dissolved oxygen and then BOD5 were in the first priority. As a conclusion, according to the the trophic state index, this dam is suitable for the development of rough fish (cyprinidae). In other words, according to the WQI index, the Azad Dam is suitable for farming of salmonids fish, but based on trophic stae index, condition is not very favorable.