An highly sensitive,stable and label free electrochemical immunosensor for the detection of 1-pyrenebutyric acid(PBA) was developed based on graphene(GS) and chitosan(CS) composites modified glassy carbon electrode (GS-CS/GCE).The proposed GS-CS/GCE was activated by the 1-ethyl-3-［3-dimethylaminopropyl］carbodiimide hydrochloride(EDC) and N-hydroxysuccinimide (NHS) (4∶1) solution in order to covalently immobilize PAHs antibody (anti-PAHs).The morphology of the GS-CS composites film was characterized by transmission electron microscopy(TEM).In phosphate buffer solution(pH 7.0) containing 0.1 mol/L KCl and 10 mmol/L K3Fe(CN)6 solution (0.1 mol/L KCl+10 mmol/L K3Fe(CN)6+0.1 mol/L PBS(pH 7.0)),the electrochemical behaviors of the modified electrode and the electrochemical properties of the immunosensor were studied by cyclic voltammetry (CV) and differential pulse voltammetry(DPV).Due to the synergistic effect of grapheme and chitosan,the peak current of GS-CS/GCE in the supporting electrolyte was largely increased,which was attributed to improve sensitivity of the immunosensor.Under the optimized conditions,the immobilization amount of antibody was significantly improved on the modified electrode,resulting in amplifying the molecular recognition ability of the modified electrodes.Because of the poor conductivity of the antybody-antigen immunocomplex,the current response of the proposed immunosensor decreased linearly with increase of PBA concentration.The linear range of theimmunosensor for PBA detection was 0.1-80 μg/L with a detection limit of 0.03 μg/L.With excellent selectivity and reproducibility,the proposed immunosensor was applied in the determination of PBA in the real sample with spiked recoveries of 90%-105%.