Abstract: In order to improve the expression yield and biological activity of aflatoxin B1 (AFB1) single chain Fv fragment (scFv), scFv genes from hybridoma cell lines 2C10 by reverse transcription method and gene splicing technology were constructed into the expression vectors pET-30a and pPICZαA respectively to compare the results. Then the constructed expression vector pET-30a-pelB-scFv was transformed into BL21(DE3) to express protein induced by IPTG. The constructed expression vector pPICZαA-scFv was linearised and transformed into Pichia pastoris by electroporation, and the transformants were induced by methanol，and the anti-AFB1 scFv was expressed. The expression proteins were purified and determined by SDS-PAGE, western blot and ELISA.The results of SDS-PAGE showed that anti-AFB1 scFvs were highly level expressed successfully, with the expression yield of about 34 mg/L in E.coli expression system and 132 mg/L in Pichia Pastoris expression system, and the goal protein is about 29 kua. The results of western blot and ELISA demonstrated that the recombinant scFv could combine with AFB1 specifically. and the sensitivity of anti-AFB1 scFv was 40 μg/mL and 35 μg/mL respectwely. Compared with anti-AFB1 scFv expressed in E.coli BL21(DE3)， the sensitivity of scFv expressed in Pichia pastoris was a little better， but there was still some room for improvement．

Key words: AFB1, single chain Fv fragment, Escherichia coli, Pichia Pastoris, ELISA