〔Abstract〕 Objective To investigate regulatory T cell(Treg), including CD8+Treg and CD4+Treg, and their relationship with NK cells in patients with hepatocellular carcinoma(HCC). Methods A total of 55 patients with HCC and 22 healthy controls were collected. Peripheral blood and liver tissues were collected from HCC patients. Peripheral blood samples were obtained from healthy controls. CD8+CD25+Treg, CD4+CD25+Foxp3+Treg and NK cells were detected by flow cytometry. Results The levels of CD8+regulatory T cells in the peripheral blood of healthy people and patients with HCC were measured, and the CD8+CD25+regulatory T cells in the peripheral blood of the patients(6.22±0.49)% were higher than those in the healthy people(4.56±0.44)%(P<0.05); The proportion of CTLA-4+CD8+regulatory T cells in cancer tissues(41.00±4.00)% was higher than that in adjacent cancers(6.23±2.75)%(P<0.05). Further comparison of CD4+regulatory T cells in cancerous tissues and adjacent cancerous tissues revealed that the proportion of CD4+CD25+FoxP3+regulatory T cells in cancerous tissues(23.28±6.78)% was higher than that in adjacent cancerous tissues(10.18±4.04)%(P<0.05). The proportion of CTLA-4+CD4+Treg cells in cancerous tissue(61.53±11.37)% was also significantly higher than that in adjacent cancerous tissue(16.33±2.38)%(P<0.05). Analysis of NK cell expression revealed that the expression ratio of NK cells in the HCC group(13.57±1.39)% was significantly lower than that in the healthy group(21.44±1.23)%(P<0.05); the proportion of NK cells in cancer tissues(7.29±10.82)% was also lower than that in adjacent cancerous tissue(25.65±3.67)%(P<0.05). The expression of NK cells in peripheral blood of HCC patients was negatively correlated with the expression of CD8+regulatory T cells(r=-0.66,P<0.05); the proportion of CD4+regulatory T cells in cancer tissue was also negatively correlated with the expression ratio of NK cells(r=-0.76,P<0.05). Conclusion The proportions of CD8+Treg and CD4+Treg with increased CTLA-4 expression in HCC patients were detected. The percentage of NK cells in PBMC and cancer tissues from HCC patients was significantly lower than that of adjacent cancerous tissues and healthy controls. The frequencies of CD8+Treg and CD4+Treg were negatively correlated with NK cells. Our results indicate that CD8+and CD4+Tregs mediate suppressive inhibition of NK cell function in HCC patients, suggesting targeting CTLA-4+Treg mediated suppression contribute to restored NK cell function.