CRC is the second leading cause of cancer-related death worldwide. There are about 700,000 people dying of CRC every year [1]. CRC is considered as one of the health care challenges, and it is related to genetic encoding and more significantly, about 70% of all CRC cases are influential by environmental aspects through a couple of years, including diets, lifestyle, metabolic syndrome and gut microecology, etc [2]. Gut microbiota consists mainly of bacteria, fungi, bacteria and viruses that populate the gut, primarily the large intestine. About 90% of gut microbiota is composed of two phyla, that is, Firmicutes and Bacteroidetes, in healthy human [3]. With the development of technology, we have a better understanding of the composition, function and metabolic characteristics of the human gut microbiota [4]. There is growing evidence that commensal bacteria of human being is the vital determinant of healthy or pathological conditions, including cancer [5]. Metagenomics and metabolomics researches stressed the double effect of the gut microbiota in tumorigenesis (either inhibit cancer or promote cancer) [6]. Gut microbiota exerts the significant effects on host by producing vitamins, metabolizing dietary compounds, inhibiting the expansion and systemic infiltration of gut pathogens [7]. Other results underline the complicacy and two-way of the association between microbiota and cancer. The progression of cancer may change the microbiota. Meanwhile, altering microbiota may influence cancer development [8]. Undoubtedly, the occurrence of CRC is also related to the function of some gut microbiota constituents whose role serves as initiator or inhibitor [9]. Although we have studied the association for many years, only a small part feature was exposed. In this essay, we will list some current results about cellular and microbial metabolism regulation in CRC, concentrating on the mechanistic association of gut microbiota metabolites and constituents with CRC prevention or treatment. The Mechanism of Gut Microbiota against Cancer Recently evidences from in vitro and animal model to clinical trials, as well as the use of selected gut microbiota for preventing or treating CRC, have demonstrated the antiproliferative activity. The selected gut microbiota mainly includes Lactobacillus, Bifidobacterium sp., Enterococcus faecalis and so on. Many studies based on human cancer cells or cell line demonstrated that gut microbiota processes the function of restraining cell proliferation or stimulating apoptosis in CRC (Table 1). In the main animal models studied from 2017 to 2019, N-methyl-Nnitrosourea (MNU), 1,2-dimethylhydrazine (DMH) and azoxymethane (AOM) were used as CRC inductor respectively. The specific gut microbiota studied in these models is shown in Table 2. In human studies conducted between 2015 and 2017, several double-blind, randomized and placebo controlled researches indicated that the addition of specific gut microbiota is effective in treating, which reduces the postoperative complications of CRC Colorectal cance...