Objective:To investigate the affinity of human single-chain variable fragment antibody against -茁-amyloid peptide(A-茁) by surface plasmon resonance(SPR) sensor. Methods:A-茁1-40 was fixed on sensing chip surface and the antibodies as E3 scfv were applied as mobile phase. Binding and separation of A-茁1-40 with the antibodies were monitored in real time. The interaction mode between antigen and antibody and the relevant dynamic parameters were determined. Results:A specific interaction between A-茁1-40 and E3 scfv or DE2B4,rather than 9E10 was detected. The binding and separation between the antigen and antibody were dynamic with a slow speed; Affinity DE2B4 with A-茁1-40 was 6.77 × 10-7 mol/L and that of E3 scfv was 5.38 × 10-6 mol/L. Conclusion:SPR is useful in determination of affinity of E3 scfv with A-茁1-40.