Silicon oxide nanowires, grown on (100) Si wafers with the oxide layer about 100nm in thickness and on quartz plates, are investigated by exposing to the same conditions in a thermal chemical vapor deposition reactor at a temperature about 860℃. Field-emission scanning electron microscopy, transmission electron microscope equipped with energy-dispersive x-ray analysis were used to characterize the samples. The results show that a large amount of amorphous silicon oxide nanowires was obtained. The morphology, size and chemical composition of the silicon oxide nanowires grown on different substrates are quite different. The reasons of forming different characteristic silicon oxide nanowires were discussed.