Abstract: A chemiluminescence immunosensor for the determination of carcinoembryonic antigen (CEA) in human serum was developed based on the strategy of immunomagnetic separation and enzymatic amplitication. Based on the specific binding of antigen-antibody, magnetic balls were used as solid-phase carrier to capture CEA, and an immune complex was formed by loading horseradish peroxidase (HRP) on the surface of immunomagnetic balls as detection marker. HRP could catalyze H₂O₂ to oxidize luminol to generate strong chemiluminescence intensity, and CEA was quantified according to the chemiluminescence intensity. As shown by the results, linear relationship between value of mass concentration of CEA and its chemiluminescence intensity was kept in the range of 0.05-80.00 μg·L^-1, with detection limit of 4.5 ng·L^-1. Test for recovery was made on the samples, giving results in the range of 97.0%-100%. Compared with other solid phase carriers and chemiluminescence immunosensors, the chemiluminescence intensity of CEA detected by this method was stronger, and it had the wider linear range and lower detection limit.