Brucellosis is a disease which is caused by Brucella .The virus can make human and livestock sick. Its transmission of wide range is easy to occur and it is large harm to human and livestock. In this paper, based on fluorescence polarization immunoassay method, a experimental system is designed. The system consists of optical, circuit components. In order to improve the sensitivity of the system, Photomultiplier tube is used as detector. A number of experiments carried out. The result shows that the design is flexible, stable which can be used widely.