Abstract: Fish is Se-enriched supplement to food for its strong bioaccumulation effect of selenium.Bosten Lake is the largest inland freshwater lake in Bohu County, Xinjiang.It is of great significance to the exploitation of fish resources and the development of local economy to probe into the selenium content,the chemical speciation and the bioaccumulation factors.Selenium content of fish muscle in 44 samples from Bosten Lake was investigated.The results showed that selenium content from high to low was as follows:white streaked fish>five black streaks>pond male fish>crucian carp>carp>silver carp>grass carp.The content was higher in the small lake area than in the large lake area in the same species.Selenomethionine (SeMet) was the dominant speciation of selenium in fish muscles, the proportion of organic selenium being 71.54%-94.08%, and the bioavailability of selenium being high.The accumulation effect of selenium and the ecological environment in food chain of aquatic organism result in the difference of bioaccumulation factor(BAF),i.e. carnivorous fish > omnivorous fish > herbivorous fish.Fish inhabiting in the bottom of water has much higher selenium content in fish muscle than those in the upper and middle layers.Natural organic se-enriched fishery should be developed in Bosten Lake due to the good quality of selenium enrichment in fish.