Rivers are one of the most important aquatic ecosystems in terms of biodiversity,The knowledge about water their quantity and quality is the most important and basic pillars of their management and sustainable protection. In addition the growth of human population in the recent decades and increase in demand for food as well as the improvement of public health have led to an increase of water consumption and pressure on fresh water resources. On the other hand, the water pollutants as a result of increased human activities have been affected the biological health conditions of rivers. Since, the most area of our country (Iran) local in the arid zone of the world, the water Rivers important for drinking, agriculture and industries. The purpose of this study is to investigate the water quality of Behesht_Abad River as one of the important sources of Karun River located in Chaharmahal Bakhtiari province. In this study, physicochemical parameters of water (temperature, pH, EC, TDS, total hardness, Percentage of oxygen saturation, BOD, nitrate and phosphate) and biological characteristics (fecal coliform, Benthic Macroinvertebrate communities) were studied in four seasons over a period of one year (Summer2018 _Summer2019). The results showed that physicochemical parameters in Beheshtabad River are constantly fluctuating under the influence of natural factors and human pollutants. One of the most important natural factors affecting the fluctuation of physicochemical parameters is air temperature fluctuations due to climate change, as well as Changes in the flow and River water flow rate due to seasonal changes in precipitation in the Beheshtabad River basin. On the other hand, the parameters of nitrate, phosphate, oxygen saturation, BOD and fecal coliforms were often influenced by human activities such as agriculture and fish ponds as well as tourism. The results of this study showed that the entry of pollutants into the river causes the extinction of sensitive species and changes in the composition of Benthic Macroinvertebrate communities. So that two sensitive families to pollution, Leuctridae and Nemouridae belong to the order plecopteria were observed only at Dehcheshmeh station. According to the results of this study Shannon_wiener and Simpson diversity indices and Margolf richness index had no significant correlation with most physicochemical parameters and were not able to distinguish infected stations from other stations as well as different seasons. In addition, according to the NSFWQI index, the water quality of Beheshtabad River was in good quality in winter and in medium quality in other seasons. The discrepancy in water quality assessment based on BMWP, ASPT and Hilsenhoff biological indicators in some seasons and stations were due to differences in the sensitivity of the mentioned indicators to different types of pollutants as well as differences in the importance of each pollutant in calculating the final index. It seems that due to the high correlation between BMWP and ASPT indices with oxygen saturation and BOD parameters, these indices have a higher ability to determine the effect of pollutants in Beheshtabad River. Therefore, it is recommended to use these indicators in Keywords: Behesht Ababd River, Bioindicators, Diversity Indices, Benthic Macroinvertebrate, NSFWQI