The aim of the study was to establish a simple method to measure antibody affinity to hepatitis B surface antigen (anti-HBs) by using a routine quantitative system to explore the significance of anti-HBs affinity. Serum samples of hepatitis B patients who had been discharged from the hospital were collected at the time of re-examination. The 60 patients with resolved HBV infection were divided into two groups based on the serological markers measured in the samples: an anti-HBs group (anti-HBs-only positive) and an anti-HBs positive with anti-HBc group. The serum samples were diluted prior to the measurement of total anti-HBs by using a commercial assay with the AxSYM device. The total anti-HBs (mIU/mL) of all dilutions were measured, and the positive data (>10mIU/mL) were transformed into logarithmic values (lgU). The relative affinity of anti-HBs was calculated and derived from the mass action formula. The absolute value of (lgU(1) - lgU(2)) positively correlated with the antibody affinity. The results indicated that affinity of anti-HBs in the samples obtained from the anti-HBs-alone positive group was statistically higher than that of the other group (P<0.05), though no significant difference was noted in regard to the total antibody activity (P>0.05). This simple approach to measurement of anti-HBs antibody affinity may serve as a new tool in clinical laboratories and contribute to the management of patients with hepatitis B.