Abstract: Simultaneous distillation-extraction method is applied to extract the volatile oils in C. japonica Choisy from North China and Cusuta chinensis Lam. from Qianshan Mountain, Liaoning Province,respectively. The volatile constituents are separated and identified by GC/MS. The twelve and eleven species of the chemical constituents in C. japonica Choisy and Cusuta chinensis Lam are identified. The results indicate that the chemical components of oils in Cusuta chinensis Lam. and C. japonica Choisy from the different location are different from each other.