Abstract: Objective To explore the correlation between the disease progression and the levels of T helper type 17(Th17)cells, regulatory T(Treg )cells in patients with non-alcoholic fatty liver disease(NAFLD). Methods A total of 25 patients with non-alcoholic fatty liver(NAFL), 25 cases with non-alcoholic fatty hepatitis(NAFSH)and 25 healthy controls were selected, The indexes related to liver lesions in the three groups ［alanine aminotransferase(ALT), aspartate aminotransferase(AST), total bilirubin(TBil), direct bilirubin(DBil)］, and four indicators of liver fibrosis ［procollagen Ⅲ(PCⅢ), type Ⅳ collagen(Ⅳ-C), laminin(LN), and hyaluronidase(HA)］ of the three groups were compared, and correlations between Th17, Treg cells as well as related inflammatory factors［Interleukin-10(IL-10), interleukin-17(IL-17)］ and degree of liver fibrosis were analyzed. Results There were no significant differences in age, sex distribution, smoking history, hypertension and family history of cirrhosis among the three groups(P>0.05). The number of patients with diabetes in the control group was seven cases, which was significantly lower than 18 cases in the NAFL group and 19 in the NASH group(P<0.05). The levels of Th17, Treg, IL-10 and IL-17 in peripheral blood showed significant between-group differences(P<0.05). The levels of ALT and AST in the NASH group were significantly higher than those in the other two groups(P<0.05). ALT level in the - NAFL group was significantly lower(P<0.05), and AST level in the NAFL group was significantly higher than that in the control group(P<0.05). The levels of TBil and DBil in the NASH group showed significant differences compared to the NAFL group and the control group(P<0.05). The levels of PCⅢ, Ⅳ-C, LN, HA and fibro-touch score in the NASH group were significantly higher than those in the other two groups(P<0.05), and HA level in the NAFL group was significantly higher than that in the control group(P<0.05). The results of correlation analysis showed that ALT, AST, TBil, DBil, PCⅢ, Ⅳ-C, LN, HA, fibro-touch score, and degree of disease had significant positive correlation with Th17 as well as IL-17(P<0.001), and significant negative correlation with IL-10 and Treg(P<0.001). Conclusion The patients with NAFLD showed a unbalanced ratio of Th17/Treg in peripheral blood. Their expression levels are highly correlated with the severity of the disease, and can be effective indicators for monitoring the progression of NAFLD.