Abstract:The composition of the volatile oil from the roots of Peuc edanum praeruptorum Dunn in Fujian province were analyzed by m eans of GC-MS technique, and 38 chemical constituents, 77.97% of total content, were identified. The main components were a-phellandrene(9.52%),á-bisabolol (8 .44%) anda-pinene (5.22%). Besides, some sesquiterpenes and their oxides such a s caryophyllene (2.62%),longifolene(2.36%) and Z-9-pentadecenol (3.72%) were al so important. The antibacterial experiments of the oil were studied on 4 tested strains in vitro， which showed that the oil had a certain an tibacterial activity against Eschedchm coli，Salmonella typhi and Shigella flexneri.