In this work, polyaniline nanofiber was synthesized. Then, polyaniline nanofiber and chitosan were dropped onto the surface of the self-prepared screen-printed electrode (SPE), respectively. After aminopyrene-BSA conjugate was immobilized on the modified electrode surface with the aid of EDC/NHS solution, the primary antibody was dropped on the modified SPE and followed by the HRP-labeled secondary antibody, thus a disposable immunosensor was developed for the rapid detection of benzo[a]pyrene based on an indirect immunoassay.