In order to improve the quality of grass carp (Ctenopharyngodon idella) flesh, C. idella cultured in a pond was treated by a micro-flow water system. The effects of treatment time (0, 1, 4, 7 and 10 d) on the nutrient composition, flavor and sensory quality of C. idella flesh were investigated. The results showed that micro-flow water treatment could significantly influence the nutrient composition, taste compounds, volatile odor compounds and sensory quality of C. idella flesh. With the prolonged micro-flow water treatment time, the content of fat and total sugar in the C. idella flesh decreased significantly, and the content of ash increased significantly, but the content of protein showed no significant difference. Taste and odor characteristics of C. idella flesh were obviously changed by micro-flow water treatment according to the results of electronic tongue (e-tongue) and electronic nose (e-nose). In addition, micro-flow water treatment significantly increased the content of IMP (inosine monophosphate), umami amino acids (Asp and Glu), sweet amino acids (Ser and Ala) and bitter amino acids (Leu and Ile) in C. idella flesh, but significantly decreased the content of total volatile base nitrogen (TVB-N) and docosahexaenoic acid (DHA). The odor score, taste score and color score of C. idella flesh at treated 4 d were significantly higher than those of C. idella samples treated at 0 d and 1 d, but had no significant difference with C. idella samples treated at 7 and 10 d. Short-term micro-flow water treatment can effectively improve the flesh quality of C. idella. The suitable treatment time is 4 days. The treated C. idella flesh not only has no fishy odor, but also has higher umami taste.