Objective To explore the relationship between the phenotype of tumor - infiltrating lymphocytes TIL and clinicopathological characteristics and gut microbiota in patients with colon cancer. Method From June 2017 to February 2023 76 colon cancer patients admitted to Taihe Hospital were collected as the colon cancer group and 76 healthy individuals who underwent physical examinations during the same period were collected as the control group. The TIL phenotype expression levels of two groups were detected fluorescent quantitative PCR was applied to detect gut microbiota and the clinical and pathological data of colon cancer patients were collected. Spearman was applied to analyze the correlation between TIL phenotype and gut microbiota. Result Compared with the control group the level of CD4 + T cell in the colon cancer group was obviously increased 28. 05± 5. 48 % vs 32. 49± 6. 13 % while the levels of CD3 + T cell and CD8 + T cell were obviously reduced 60. 47 ± 6. 53 % vs 53. 17 ± 6. 37 % 30. 69±6. 38 % vs 24. 85 ± 6. 42 % P < 0. 05 . According to the median values of CD3 + T cell 52. 62% CD8 + T cell 25. 87% and CD4 + T cell 31. 94% colon cancer patients were divided into 38 cases with high expression of CD3 + T cell 38 cases with low expression of CD3 + T cell 38 cases with high expression of CD8 + T cell 38 cases with low expression of CD8 + T cell 38 cases with high expression of CD4 + T cell and 38 cases with low expression of CD4 + T cell. There were lymph node metastasis the higher the degree of tumor differentiation the higher the TNM stage and the difference between high and low expression of CD3 + T cell CD8 + T cell and CD4 + T cell was statistically significant χ 2 = 5. 330 4. 659 6. 786 χ 2 = 7. 962 10. 483 4. 343 χ 2 = 11. 120 7. 280 13. 300 P<0. 05 . Compared with the control group the numbers of Bacteroides fragilis Escherichia coli and Enterococcus in the colon cancer group increased obviously 6. 58 ± 0. 83 lgN/ g vs 8. 59 ± 1. 36 lgN/ g 7. 36 ± 1. 04 lgN/ g vs 9. 73 ± 1. 25 lgN/ g 7. 21±1. 08 lgN/ g vs 9. 28±1. 74 lgN/ g while the numbers of Lactobacillus and Bifidobacterium decreased obviously 8. 85±1. 46 lgN/ g vs 6. 34± 1. 22 lgN/ g 8. 94± 1. 09 lgN/ g vs 6. 17± 1. 32 lgN/ g P< 0. 05 . Spearman correlation analysis showed that Bacteroides fragilis Escherichia coli and Enterococcus were negatively correlated with the proportion of CD3 + T cell and CD8 + T cell in colon cancer patients r = - 0. 482 - 0. 459 - 0. 532 r = - 0. 438 - 0. 472 - 0. 508 P < 0. 05 Lactobacillus and Bifidobacterium were positively correlated with the proportion of CD3 + T cell and CD8 + T cell r = 0. 581 0. 507 r = 0. 536 0. 467 P<0. 05 Bacteroides flimsii Escherichia coli and Enterococcus were positively correlated with the proportion of CD4 + T cell r = 0. 483 0. 495 0. 461 P<0. 05 and Lactobacillus and Bifidobacterium were negatively correlated with the proportion of CD4 + T cell r = -0. 563 -0. 579 P<0. 05 . Conclusion The phenotypes of CD3 + T cell CD8 + T cell and CD4 + T cell in TIL of colon cancer patients have certain relationship to the clinicopathological characteristics and gut microbiota.