The essential oils which extracted by hydro distillation method was studied by GC-MS and evaluation methods during Chimonanthus praecox (L.) Link booming. The number and the contents of fragrant components of essential oils were changed during aroma releasing.The components of fragrant contents of essential oils were identified by searching the standard NIST05 database during the following three stages (buds, early spread, spread),and the variation of fragrant contents was studied as well. Results showed that the main fragrant components of different booming stages(buds, early spread, spread and final flowers) was approximately the same, whereas the relative percentage of linool increased significantly from the buds from early spread, arrived at the maximum of 11.72%.