Abstract: In aquaculture, selenium has been shown to improve the immune and antioxidant capacity of aquatic animals. As a kind of new style protein resource, cottonseed protein concentrate plays a crucial role in aquaculture industry, however, the antinutritional factors (such as gossypol) seriously hindered the application of cottonseed protein concentrate in aquatic feed. Therefore, the purpose of this study was to investigate the effects of adding yeast selenium (YS) to the diet that containing cottonseed protein concentrate on the growth performance and muscle quality of grass carp (Ctenopharyngodon idella). Four isonitrogenous and isolipidic diets were designed: 0, 0.3, 0.6 and 0.9 mg/kg YS were added to the diet containing cottonseed protein concentrate, and corresponding named YS0, YS3, YS6 and YS9, respectively. A total of 240 healthy grass carp with similar size (initial weight: 309.74±0.36 g) were randomly distributed into 12 net cages in the pond. Each of the experimental diets was randomly fed triplicate cages for 56-day three times per day (9:00, 13:00 and 17:00). The results showed that: (1) In terms of growth performance, compared with YS0 group, there was no significant difference in growth performance between YS3 and YS6 groups (P>0.05), but the final body weight (FBW), weight gain rate (WGR) and specific growth rate (SGR) of YS9 group were significantly reduced (P<0.05); (2) In terms of muscle quality, compared with YS0 group, the crude protein content, selenium content, hydroxyproline content and hardness of grass carp muscle in YS3 group were significantly increased (P<0.05), and the fiber diameter and cohesiveness of muscle were significantly decreased (P<0.05). The study indicated that the addition of YS to the diet containing cottonseed protein concentrate (the selenium content of the diet was 0.6 mg/kg) had no significant effect on the growth performance of grass carp, and flesh quality were significantly improved. However, exceeded dietary YS had negative influence on the growth performance of grass carp. This study provides a theoretical basis for further application of cottonseed protein concentrate in aquatic feed.