A new electrochemical immunosensor for fast determination of ractopamine (RAC) is fabricated based on pristine graphene (PG). The PG provides a microenvironment beneficial the immobilization of RAC, promotes the electron transfer, and raises the sensitivity of the immunosensor. The free RAC in solution can be effectively measured based on the competitive immunoreaction between RAC-antibody and RAC. The calibration graph shows linearity over the concentration ranges of 0.1-10 and 10-4000 ng mL (1). The proposed immunosensor displays a satisfactory stability, selectivity, and reproducibility and has been applied to the quantificational detection of RAC in real pork samples. (C) 2017 Elsevier B.V. All rights reserved.