Objective:To study the correlation of serum monokine induced by IFN-γ(Mig)and interleukin9(IL-9) levels to HBV pre-C/BCP mutation and their influences on the response to interferon therapy in patients with HBeAg-positive chronic hepatitis B(CHB).Methods:A total of 110 cases of HBeAg-positive CHB patients in the People′s Hospital of Jianyang City were retrospectively analyzed from February 2015 to February 2018, and all received pegylated-IFN-αtherapy.Before treatment, the gene fragment of HBV pre-C/BCP region was amplified and the patients were divided into two groups: wild type group (61 cases) and mutant group (49 cases). The difference of serum MIG, IL-9 and antiviral treatment effect between the two groups were compared.Results:The serum IL-9 of mutant group before treatment ((10.8±1.9) ng/L)was significantly higher than that of wild group((8.3±1.7) ng/L) ( P<0.05). The complete response rate of mutation group was 46.9% (23/49) after 48 weeks of treatment, which was significantly higher than that of wild group(16.4% (10/61)) (χ 2=7.083, P=0.018). After 24 weeks of treatment, the serum Mig of patients with HBsAg decrease>1 lg 10 in mutation group before treatment was significantly higher than HBsAg decrease≤1 lg 10 ((129.2±37.9) ng/L vs.(91.5±25.7) ng/L)( P<0.05). The serum IL-9 in the mutant group were(8.8±1.9) ng/L and (8.9±1.6) ng/L at 12 and 24 weeks after treatment respectively, which were significantly lower than that before treatment (all P<0.05). Conclusion:The high expression of IL-9 in serum of CHB and HBeAg positive patients before treatment is closely related to the variation of HBV pre-C/BCP region, and the expression of IL-9 is not related to the antiviral effect of interferon.The high expression of MIG in patients before treatment may be more beneficial to the antiviral effect of interferon in patients with HBV pre-C/BCP region variation.