ObjectiveTo explore the influence of enhanced recovery after surgery (ERAS) on intestinal flora in patients with colorectal cancer.MethodsBy convenient sampling method, 60 patients with colorectal cancer were selected from August 2018 to December 2019 in the Department of Gastrointestinal Surgery of West China Hospital of Sichuan University and randomly divided into ERAS group and traditional treatment group (traditional group). Among them, the perioperative clinical management was carried out according to the ERAS management and traditional treatment process in the the ERAS group and in the traditional group, respectively. The fresh fecal samples were collected within 24 h after admission and the first natural defecation after operation. The bacterial 16 Sr DNA V3–V4 region was sequenced by Illumina MiSeq sequencer, and the results were analyzed by bioinformatics.ResultsA total of 60 patients with colorectal cancer were included, 30 cases in the traditional group and 27 cases in the ERAS group (3 people temporarily withdrew from the study). There were no significant differences in the basic informations between the two groups (P>0.05). ① Before or after operation, there were no significant differences in Shannon index and Simpson index between the two groups. The difference between preoperative and postoperative comparison in the same group was also not statistically significant (P>0.05). ② Beta diversity analysis showed that there was no significant difference in community composition between the traditional group and the ERAS group before operation, and there was a clear boundary between the traditional group and the ERAS group after operation. ③ At the phylum level, compared with the preoperative abundance, the postoperative abundance Firmicutes decreased by 26.5% and 5.5% in the traditional and ERAS group, respectively; Bacteroidetes increased by 21.6% and 4.7% in the traditional and ERAS group, respectively; Proteobacteria increased by 7.2% and 2.2% in the traditional and ERAS group, respectively. At the genus level, compared with the preoperative abundance, the postoperative abundance of Bacteroides in the traditional group increased by 17.6% and in the ERAS group decreased by 1.6%; Bifidobacterium decreased by 1.8% and 1.3% in the traditional group and in the ERAS group, respectively.ConclusionsERAS does not affect species diversity of intestinal flora. Although ERAS has some damage to structure of intestinal flora, it is weaker than traditional process, so it is more conducive to reconstruction and restoration of intestinal microecological environment.