Ctenopharyngodon idella and Ictalurus punctatus raised in ponds were subjected to short-term fasting in the circulating water system for 28 d to investigate the impact of fasting on the edible quality of commercial fish. The nutritional composition of muscles, as well as the texture characteristics, hydraulic properties, and morphological changes of the dorsal muscles were also examined under various fasting times and body segments of the fish. Varied body forms of grass carp and channel catfish had significantly varied amounts of muscle nutrients. The muscle crude fat level of grass carp and channel catfish significantly decreased after 14 d-fasting intervals at(P＜0.05). The crude protein content of channel catfish grew before 7 d-fasting and thereafter fell(P＞0.05), while the crude protein content of grass carp started to decline at 28 d. Muscle glycogen levels in both fish dropped before 7 d-fasting and then rose(P＞0.05). The dorsal muscles were the least hydraulic in grass carp and channel catfish after short term-fasting of 28 d and 21 d, respectively(P＜0.05). Fasting for 28 d in grass carp and 21 d in channel catfish resulted in a large increase in the hardness and chewiness of the dorsal muscles(P＜0.05), a significant decrease in the area of the muscle fibres(P＜0.05), an increase in the density of the muscle fibres, and a significant decrease in the number of lipid droplets in the muscle fibres. This experiment demonstrated that short-term fasting might greatly increase the flesh quality of grass carp and channel catfish in the circulating water system, which the grass carp in 28 d-fasting and channel catfish in 21 d-fasting were the best. It is feasible to use this method to improve the fish quality in production practice. And the experimental results provide a theoretical reference for the improvement of fish food quality. [Chinese Fishery Quality and Standards, 2023, 13(5)：17-30]