An electronic detection method for DNA molecules based on an extended gate field effect transistor (EGFET) sensing chip has been presented in this paper, which consists of one gold plate electrode for molecule recognition and FET part for signal transduction. The DNA probe was prepared by first immobilization of a thiolated single-stranded oligonucleotide (T1) and then an alkanethiol such as 6-hydroxy-1-hexanethiol (6-HHT) on the gold plate. A fast cyclic voltammetry (FCV) was applied to quantification of DNA molecules by using a cathodic peak around -1.3 V at a electrode reaction, corresponding to reductive desorption in strong alkali solution. By using a 70.7 mV DC voltage onto a Ag/AgCl reference electrode, the electronic signals of EGFET were applied to detection of DNA molecules and its hybridization, and the corresponding hybridization efficient was estimated to be about 37.5%. About 1 ~ 4 DNA molecules per 100 nm2 on the Au substrate of EGFET could be counted, showing a promising sensing technique for bio-molecule.