[en] A novel flow-injection chemiluminescence method for the determination of DNA at ultra-trace level has been established. In 0.8 M sulfuric acid media, the chemiluminescence of the rhodamine B-cerium (IV) or Ce(IV) system is enhanced by DNA, activated previously by imidazole-HCl buffer solution (pH 7.0). The enhanced intensity of chemiluminescence is in proportion to log DNA concentration 1.0x10^-8 to 0.1 μg ml^-1 for herring sperm DNA and 2.0x10^-6 to 0.2 μg ml^-1 for calf thymus DNA with 3σ detection limits of 8.3x10^-9 μg ml^-1 for herring sperm DNA and 3.5x10^-7 μg ml^-1 for calf thymus DNA, respectively. The relative standard deviation for 1.0x10^-4 μg ml^-1 herring sperm DNA was 0.99% and 2.0x10^-3 μg ml^-1 for calf thymus DNA was 1.1% (n=11). Using the optimized system, DNA contents in six synthetic samples has been determined with recoveries of 99.5-109.0%. The possible mechanism has also been studied in this paper