Objective: To study the volatile oil composition differences from Four of Cyperus rotundus of Jianchangbang and raw materials of Cyperus rotundus, and discuss the influence of Jianchangbang processing method on the volatile components. Method: The comparative analysis was performed with HPLC and GC-MS on the constituents of volatile oil of Rhizoma Cyperi before and after processing. Result: the HPLC method showed that the principal component of Four of Cyperus rotundus and raw materials Rhizoma Cyperi (relative peak area of more than 10% )...