Surface plasmon resonance (SPR) was used to detect sulfadiazine (SD) in milk.SD-BSA conjugate as sensitive probe was immobilized onto the surface of a biochip for the development of a competitive inhibition immunoassay to detect SD in milk using SPR.The calibration curve was established.The limit of detection for SD was 3.41 ng/mL,and the recovery of spiked samples was in the range of 71％-120％.The proposed SPR method proved to be sensitive and accurate.