Occurrence of processes such as thermal stratification and nutrition in reservoirs leads to a severe drop in water quality and a lack of optimum levels for various uses and it threatens the life of the aquatic ecosystem. Today, the reservoir of many dams of Iran faced with water quality problems and lowering oxygen dissolution in dehydrated and warm seasons are perhaps the most important negative effects of such reservoirs. Simulation models of Water tank quality are a good tool for predicting water quality, estimating the effects of the contamination of the quantifying the extent and severity of environmental impacts after starting the operation considering the physical and climatic conditions of the reservoir and flow of the river inlet. The studied dam is in the upper reservoir of the Koran Bozan Dam in about 65 km south-east of Kermanshah city. Since there are several sources of pollution on the passage of the river upstream to the dam, the purpose of this study is to investigate the simulation of thermal stratification and soluble oxygen in the dam in line with the environmental studies of the Garsha dam to prevent the damaging effects of dam construction on this region which this study was carried out in 1393. In this regard, at first, the hydrodynamic model of the reservoir of the Garsha Dam was constructed and then calibrated with CE QUAL W2 software and it was used in order to simulate the heat layering and the dissolved oxygen in the dam. The results indicate that thermal stratification is in summer.