Objectives To investigate contents and clinical significances of CD19+IL-10+ B cell and its subsets in peripheral blood monouclear cell (PBMC) and cancer tissue of patient with colorectal cancer (CRC). Methods Thirty-eight patients with CRC underwent surgery from November 2017 to November 2018 in this hospital were enrolled as a trail group. The proportions of CD19+IL-10+ B cell, CD19+IL-10+CD24hiCD38hi B cell, CD19+IL-10+CD24intCD38int B cell, and CD19+IL-10+CD24hiCD38– B cell in the CD19+ B cells in the PBMC, cancer tissue and paracancer tissue of these patients were detected by the flow cytometry. Thirty-seven healthy volunteers were selected as a control group and the same cell types same as the trail group were detected by the same method in the PBMC only. Results ① The contents of CD19+IL-10+ B cell and CD19+IL-10+CD24hiCD38hi B cell of the PBMC in the trail group were significantly higher than those in the control group (t=9.09, P<0.01; t=9.36, P<0.01, respectively), which of the cancer tissues in the trail group were significantly higher than those in the corresponding paracancer tissues (t=11.67, P<0.01; t=19.64, P<0.01, respectively), while the content of CD19+IL-10+CD24hiCD38– B cell of the PBMC in the trail group was significantly lower than that in the control group (t=6.15, P<0.01). But the CD19+IL-10+CD24intCD38int B cell had no significant difference of the PBMC between these two groups (t=1.78, P=0.08). ② The contents of CD19+IL-10+ B cell and CD19+IL-10+CD24hiCD38hi B cell of the PBMC in the CRC patients with stage Ⅲ+Ⅳ were significantly higher than those in the CRC patients with stage Ⅰ+Ⅱ (t=5.39, P<0.01; t=3.13, P<0.01, respectively). The others all had no significant differences (P>0.05). Conclusion CD19+IL-10+ B cells are significantly increased in PBMC and cancer tissue of patient with CRC and with advanced CRC (TNM stage Ⅲ+Ⅳ), further more, main increasing subgroup of CD19+IL-10+ B cell is CD19+IL-10+CD24hiCD38hi B cell, which indicates that CD19+IL-10+ B cell and CD19+IL-10+CD24hiCD38hi B cell might participate in tumorigenesis and tumor progress of CRC.