Abstract: After the interaction of fluorescein and neutral red with DNA, the fluorescence transfer system developed for nucleic acids had been studied by using fluorimetric, ultra-violet methods. Experiments revealed that nucleic acids could enhance remarkably the fluorescence intensity of Fluorescein with fluorescence quenching of neutral red in the presence of DNA. Under optimum conditions, the calibration graphs are linear over the range of 0.25～6.25 μg/mL for herring sperm DNA, 0.10～4.00 μg/mL for salmon DNA, 0.10～5.00 μg/mL for calf thymus DNA with the detection limit (3σ/K) being 0.021 μg/mL, 0.023 μg/mL and 0.025 μg/mL respectively. In the determination of nucleic acids in synthetic samples, the value of RSD for several replicates is less than 4.2% and the recoveries range between 91.3% and 101.4%.