A new method of preparing fiber-optic DNA biosensor and its array for the simultaneous detection of multiple genes is described. The optical fibers were first treated with poly-1-lysine, and then were made into fiber-optic DNA biosensors by adsorbing and immobilizing the oligonucleotide probe on its end. By assembling the fiber-optic DNA biosensors in a bundle in which each fiber carried a different DNA probe, the fiber-optic DNA biosensor array was well prepared. Hybridization of fluorescent- labeled cDNA ofp53 gene,N-ras gene andRb1 gene to the DNA array was monitored by CCD camera. A good result was achieved.