Objective To analyze hepatitis B virus(HBV) infection stage in single nucleic acid test(NAT)reactive blood donors.Methods Blood donor samples were screened routinely for HBV DNA by using transcription-mediated amplification(TMA) NAT and quantitative polymerase chain reaction(PCR).Then serum markers of HBV were also detected.The HBV infection stage was analyzed.Results Among the 225 single NAT reactive samples,78(34.67%) were identified to be reactive for HBV DNA by TMA NAT discrimination test and/or PCR test,of which 63(82.89%) were occult HBV infection(OBI),13(17.11%) were probably window period infection(pWP),and 2 cases could not be classified for infection stage.Among the OBI samples,49 samples(77.78%) were with HBV DNA concentration less than 20 IU/mL,whereas,there were only 4 samples(30.77%) in pWP samples.The 225 samples were classified into three groups according to the S/CO of NAT, including 1-<6 group,6-<10 group and 10-17 group, the confirmed HBV DNA positive rates of which were 13.11%,13.64% and 47.18%,and the positive rate of 10-17 group was higher than 1-<6 group and 6-<10 group(P<0.05).In all 63 OBI samples,there were 8(12.70%),3(4.76%) and 52(82.54%) samples were classified into S/CO 1-<6,6-<10 and 10-17,respectively.All of the 13 pWP samples were with NAT S/CO of 10-17.Conclusion Part of single NAT reactive blood donors could be with HBV infection,of which OBI might be popular than pWP, with very low concentration of HBV DNA.Deferral of single NAT reactive blood donors could reduce transfusion-transmitted HBV infection.