Abstract:  Objective To explore the applicability of ELISA for HBsAg detection in infants. Methods The HBsAg weakly positive pooled serums were used to evaluate the precision of ELISA. The serial dilutions of pooled serum were detected and valued by CMIA to analysis the LOD of ELISA in measuring HBsAg. The 350umol/L bilirubin or 5g/L hemoglobin were added into serum to perform interference test. The serum samples from infant (<1 year) that were HBsAg positive tested with CMIA were detected with ELISA to evaluate the diagnostic sensitivity, specificity of ELISA. Results As to 1 ng/mL HBsAg weakly positive level sample, the coefficient of variation of ELISA was 18.91% and the LOD was 0.125 ng/mL. The addition of 350 umol/L bilirubin or 5 g/L hemoglobin had no significant effect on the accuracy of test results. As to less than 0.25 ng/mL HBsAg weakly positive level sample, the consistency of detection results by ELISA and CMIA was 30.3%, whereas on the level above 0.5 ng/mL, the consistency reached 95.6%. The diagnostic sensitivity of ELISA was 87.14%, and the negative predictive value was 79.07%. Conclusion Despite the sensitivity of the ELISA method is worse than that of CMIA, however, on weakly positive level, the analytical performance of ELISA still acceptable. ELISA is a good screening method.