An amperometric ascorbic acid biosensor based on ascorbate oxidase (EC 1.10.3.3) from cucumber(Cucumis sativus L) for the specific determination of L-ascorbic acid in agricultural applications was successfully developed using the PEDOT-modified electrode,which electrosynthesized potentiostatically in 0.05 mol L-1 phosphate buffer solution (PBS,pH=6.0) containing 3,4-ethylenedioxythiophene (EDOT) monomer,ascorbate oxidase and a biocompatible amino acid-based surfactant Sodium N-lauroylsarcosinate (SLS).The analytical performances and dynamic ranges of this electrochemical biosensor were determined,which showed good sensitivity,long term stability,and excellent reproducibility.Optimization of measurement parameters such as applied potential,surfactant concentration,polymer film thickness,enzyme kinetics,temperature,pH value,morphologies of the enzyme were investigated and discussed in detail.