We found that the phenotype, absolute counts, and function of NK cells were significantly altered in the peripheral circulation of patients with CRC, mainly manifesting as a decrease in the absolute counts of NK cells, a change in the frequency of NK cell subsets, a decrease in the percentage and MFI of intracellular IFN-γ of NK cells, and a significant decrease in the positive percentage of granzyme B and perforin on the cell surface. This evidence concerns the gene PRF1 and colorectal carcinoma.