The gut microbiota plays an important role in the development and progression of colorectal cancer (CRC). To learn more about the dysbiosis of carcinogenesis, we assessed alterations in gut microbiota in patients with CRC. A total of 23 subjects were enrolled in this study: 9 had CRC (CRC group) and 14 had normal colons (normal group). The microbiome of the mucosal-luminal interface of each subject was sampled and analyzed using 16S rRNA gene amplicon sequencing. We also used Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) to predict microbial functional profiles. The microbial composition of the mucosal lumen differed between the groups, and the presence of specific bacteria may serve as a potential biomarker for colorectal carcinogenesis. We identified a significant reduction in Eubacterium, which is a butyrate-producing genera of bacteria, and a significant increase in Devosia in the gut microbiota of CRC patients. Different levels of gut microflora in healthy and CRC samples were identified. The observed abundance of bacterial species belonging to Eubacterium and Devosia may serve as a promising biomarker for the early detection of CRC.