The aim of this study was to investigate the environmental impacts of fish cage culture on some biological and non-biological parameters. The study area in Mazandaran Province has been located in two cage fish farming centers in the cities of Klarabad and Abbas Abad in south of Caspian Sea. Each center had four circular polyethylene floating cages of 2500 cubic meters (20 meters in diameter and 8 meters in height). The initial storage rate of rainbow trout for each cage was 5 tons or 20,000 pieces with a weight range of 240-260 grams. The final harvesting rate of each cage was 15 tons with a weight range of 700-900 grams.The fish cage culture was carried out for 5 months (late December 2014 to mid-May 2015). The sampling was carried out in January and March 2014 and in May and august 2015 around the cages (shadow cage, 50 meters, 100 meters and 1000 meters) in three geographical directions (east, west and south). Sampling was maked of biological organisms (macrobenthos, plankton and bacteria) and non-biotic parameters (water and sediment). In this study, water quality index, trophic level index, biological indices of planktonic and macrobenthos were determined and analyzed. The results showed that there were no definite and regular changes influenced by fish farming on the cage environment in the two sites of klar Abad and Abbas Abad. It seems that this situation can be attributed to the hydrological conditions of the area, the low volume of fish culture, the short fish culture period, the proper depth of water for the establishment of cages and turns and currents water, especially in different directions. Therefore, the sites were used for the first fish culture period, the accumulation of nutrients around the cages did not change immediately in the ecosystem structure of these areas. Of course, there were changes in biological organisms and non-biological parameters during different sampling periods, which was the result of seasonal changes and environmental conditions in the area. Therefore, it is recommended that an environmental impact assessment be carried out for fish cage cultur in large scale farms or farms with several culturer experiences. Iranian Fisheries Science Research Institute Published