Objective: The volatile oils of Fructus Aurantii Immaturus are analyzed to verify whether the chemical constitutes are various in different species. Method: The Fructus Aurantii Immaturus samples of Citrus aurantium and Citrus sinensis are collected from Chongqing

and each species have two batches.The volatile oil which obtained by the method of water steam distillation are analyzed by GC-MS

then the chemical constitutes of volatile oil are identified by Data Base Retrieval and by comparing with the relative standard mass spectrum data

and the relative amount of each constitute is calculated by area normalization method. Result: Twenty-nine constitutes are identified in two batches of C. aurantium

and account for 97.4% in total oil.Thirty-eight constitutes are identified in two batches of C.sinensis

and account for 99.07% in total oil.Among them

twenty-four constitutes are common in the two species

and nineteen constitutes are different.Meanwhile

the content of each constitute exhibit some different between the two species.In the same species of Fructus Aurantii Immaturus

the chemical constitutes are no different in two batches. Conclusion: The chemical constitutes are obviously different between C.aurantium and C.sinensis.