A nanoimmunosensor for rapid quantification of benzo(a)pyrene (BaP) in food was constructed by modifying the glassy carbon electrode (GCE) with 2.0 G polyamidoamine (PAMAM), graphene (GS), and a 1-butyl-3-methylimidazolium tetrafluoroborate composite film and by immobilizing the antibody against polycyclic aromatic hydrocarbons (PAHs) on the surface of the GCE. On the basis of the specific immune reaction between the anti-PAH antibody and antigen, the effects of the immune response on the immunosensor response current were studied by cyclic voltammetry and differential pulse voltammetry using K3[Fe(CN)6] as the probe in phosphate buffer (pH=7.0) containing 1 mmol/L K3[Fe(CN)6] and 0.1 mmol/L KCl. At optimized experimental parameters, the peak response current of the immunosensor decreased with the increasing BaP concentration, and the response current showed a linear relation with the concentration of BaP in the range 0.1–100 ng/mL, with a detection limit of 0.03 ng/mL (S/N=3). The prepared anti-PAH/PAMAM/GS/IL/GCE immunosensor showed excellent stability and reproducibility. The newly developed method was applied to analysis of BaP content in peanut and rapeseed oil samples, and the recovery rate was in the range of 94.46~103.36%. The results were generally consistent with those obtained by high-performance liquid chromatography (HPLC) method; therefore, the proposed method is feasible for rapid quantification of BaP in grain- and oil-related foods.