Traditional Southern blot, as the golden standard to detect DNA, is widely used in molecular biology. However, its operation process has some significant disadvantages, such as radioactive contamination, complex procedures, time-consuming. Some new methods developed in recent years need expensive equipments and also have the defects of complex procedures and time-consuming. The paper described a method to detect DNA quickly by liquid hybridization. The probe used is a fragment of DNA sequence labeled by FITC-12-dUTP. The whole process includes four steps: probe preparation, hybridization, electrophoresis and signal detection. The comparative experiments using the single strand DNA probe and the double strand DNA probe indicated that the sensitivity of single strand DNA probes, which could detect 0.38μg (1.82×10-13 mol) plasmid, is 2.1 times than that of the double strand DNA probes which could detect 0.8 μg(3.64×10-13 mol) plasmid. The total procedure is simple and can be completed in 3 h.