Abstract: 【Objective】 The aim of this study was to investigate the mechanism of Clostridium butyricum in regulating the growth performance and muscle quality of grass carp（Ctenopharyngodon idella）under chronic alkaline stress, and to provide theoretical reference for improving grass carp farming in alkaline water environment. 【Method】 The experiment was conducted with control（CON）, 20 mmol/L alkalinity（20 mmol/L）, 40 mmol/L alkalinity（40 mmol/L）, 20 mmol/L alkalinity + Clostridium butyricum（20 mmol/L+Clostridium butyricum） and 40 mmol/L alkalinity + Clostridium butyricum（40 mmol/L+Clostridium butyricum）. After the experiment, growth performance indexes of grass carp were measured. Muscle blocks were cut from the back white muscle of grass carp, and the muscle textrue characteristics were measured. Grass carp back muscle samples were collected and stained with hematoxylin-eosin for muscle tissue structure observation. Grass carp back muscle samples from different treatment groups were taken to calculate the centrifugal loss rate, cooking loss rate and storage loss rate. Grass carp were anesthetized with MS-222, and blood samples were collected from the caudal vein of grass carp using a 1 mL sterile syringe to detect serum biochemical indexes concentration. 【Result】 The results of growth performance indexes showed that the final body weight, weight gain rate and specific growth rate of grass carp in the 20 mmol/L and 40 mmol/L groups were significantly lower than those in the CON group（P＜0.05, the same below）, while the feed coefficient was higher than that in the CON group, especially the feed coefficient in the 40 mmol/L group was significantly higher than that in the CON group. The final body weight of grass carp in the 20 mmol/L+Clostridium butyricum group was higher than that in the 20 mmol/L group, the final body weight of grass carp in the 40 mmol/L+Clostridium butyricum group was not significantly different from that in the 40 mmol/L group（P＞0.05）. The visceral body index of grass carp in the 40 mmol/L+Clostridium butyricum group was significantly higher than that in the 40 mmol/L group, and basically recovered to the CON level. The results of muscle texture properties showed that the muscle hardness, adhesiveness and chewiness of grass carp in the 40 mmol/L+Clostridium butyricum group were higher than those in the 40 mmol/L group. The results of muscle histological observation showed that compared with the 20 mmol/L group, the muscle tissue structure of grass carp in the 20 mmol/L+Clostridium butyricum group was slightly improved but still damaged, and the muscle fiber arrangement was improved but not completely recovered. Compared with the 40 mmol/L group, the muscle tissue structure of grass carp in the 40 mmol/L+Clostridium butyricum group was tighter, and the muscle tissue was greatly improved, but still damaged. The results of muscle water holding capacity showed that the cooking loss rate of grass carp muscle in the 40 mmol/L group was the lowest, and the storage loss rate of grass carp muscle in the 20 mmol/L+Clostridium butyricum and 40 mmol/L+Clostridium butyricum groups was significantly lower than that in the 20 mmol/L and 40 mmol/L groups. The results of serum biochemical index detection showed that compared with the CON group, the urea concentration in the 20 mmol/L and 40 mmol/L groups was significantly reduced. The concentrations of alanine aminotransferase in the 20 mmol/L, 40 mmol/L, 20 mmol/L+Clostridium butyricum and 40 mmol/L+Clostridium butyricum groups were all lower than those in the CON group, and the concentrations of uric acid were all significantly lower than that in the CON group. Compared with CON group, blood glucose concentration of grass carp increased in 20 mmol/L and 40 mmol/L groups, and the blood glucose concentration increased further after the addition of Clostridium butyricum. The concentrations of serum albumin, globulin and total protein in the 40 mmol/L group were higher than those in the 20 mmol/L group, and the concentrations of albumin, globulin and total protein decreased after the intervention of Clostridium butyricum. The concentration of high-density lipoprotein in the 40 mmol/L group was higher than that in the 20 mmol/L group, and the concentration of high-density lipoprotein decreased after the addition of Clostridium butyricum. Compared with CON group, low-density lipoprotein and total cholesterol concentration of grass carp increased in 20 mmol/L and 40 mmol/L groups, and the concentrations decreased after the addition of Clostridium butyricum. 【Conclusion】 High alkaline environment can weaken the growth performance and physiological function of grass carp by disrupting nutrient metabolism, reducing intestinal health level and damaging muscle tissue. Clostridium butyricum can alleviate the negative effects of alkaline stress on grass carp within a certain range by regula-ting nutrient metabolism, improving intestinal health and enhancing stress resistance, but in a high alkaline environment, the regulation ability of Clostridium butyricum is limited.