Abstract: The bacteria community in the gastrointestinal tract of fish has been the subject of numerous studies. However, most of those researches have focused on the molecular ecology of intestinal microbiota. Few studies pay attention to the bacterial culture, especially to the culture of the anaerobic intestinal bacteria, which leads to poor description in anaerobic autochthonous bacteria of gut. In this study, we investigated the autochthonous microflora of intestinal mucosa in grass carp (Ctenopharyngodon idellus) with the culture dependent method. The bacterial numbers in foregut, midgut and hindgut of the fish were 3.17×10⁴, 1.63×10⁵ and 1.79×10⁸ cfu/g, respectively. A total of 274 bacterial isolations were sequenced and identified as genus Bacteroides, Cetobacterium, Fusobacterium, Aeromonas, Shewanella, Bacilluss, Pantoea and Citrobacter. 9.1% of which were obligate anaerobic bacteria and the others were facultative bacteria. The anaerobic bacteria, Bacteroides paurosaccharolyticus and Bacteroides. Eggerthii, were only found in midgut and hindgut, while Cetobacterium somerae and Fusobacterium varium were only found in hindgut. The facultative bacteria existed in the whole gut, among which Aeromonas hydrophila was dominant. Our results suggest that species and quantities of intestinal bacterial vary with the segments of C. idellus, and hindgut presents higher bacterial abundance and diversity.