OBJECTIVE To explore relationship between HBV DNA level and peripheral blood follicular helper T lymphocyte (Tfh) in patients with chronic hepatitis B (CHB) and its significance. METHODS HBV DNA levels of 179 cases of CHB patients with positive HBV DNA, positive HBeAg and positive human leukocyte antigen(HLA)-A2 were tested with real time fluorescent quantitative PCR. Tfh and HBV specific CTL were tested with flow cytometry. IL-21 was also tested. 179 cases of CHB patients were divided into group A and group B based on HBV DNA levels, 86 cases in group A, HBV DNA levels were 10(4)-10(5) copies/ml, 93 cases in group B, HBV DNA levels were 10(6)-10(7) copies/ml. Above testing indexes of the two groups were compared. RESULTS HBV DNA levels of group A were (4.85 +/- 0.37) log10 copies/ml, HBV DNA levels of group B were (6.83 +/- 0.31 ) log10 copies/ml, t = 27.31, P < 0. 001; Tfh of group A was (5.96 +/- 1.59)%, higher than that of group B (3.71 +/- 2.15)%, t = 4.92, P < 0.01; IL-21 of group A was (42.61 +/- 15.11)ng/L, higher than that of group B (14.91 +/- 3.15) ng/L, t = 8.62, P < 0.01; HBV specific CTL of group A was (0.36 +/- 0.08)%, higher than that of group B (0.18 +/- 0.06)%, t = 19.99, P < 0.001. CONCLUSIONS Serum HBV DNA level of CHB patients is related to the level of peripheral blood Tfh level: patients with low HBV DNA level have high Tfh level, high IL-21 level and high HBV specific CTL level. Patients with high HBV DNA level have low Tfh level, low IL-21 level and low HBV specific CTL level. The mechanism of baseline HBV DNA level affecting anti-viral therapy may be related to Tfh level.