Abstract: Two anti CEA monoclonal antibodies are used, one is coated on the microtiter plate, the other is labeled with horseradish peroxidase(HRP), enzyme linked immunosorbent assay(ELISA) kit for CEA is preparation based on two step assay. TMB H 2O 2 solution is used as the substrate of HRP. The sensitivity of the assay is 0.4 μg/L. The intra and inter CVs are lower than 10.0% and 15.0% respectively. The analytical recoveries are ranged from 99.4% to 108.7%. The reference cut off value of normal serum( n=118 )is 10.0 μg/L.