Abstract: Four diterpenoids kamebakaurin (Ⅰ), excisanin A (Ⅱ)， rabdokunmin C (Ⅲ) and kamebanin (Ⅳ) in Rabdosia excisa in different growth periods were determined via RPHPLC. The separation was performed on a ZORBAX Extend C18 column (250 mm × 4.6 mm， 5 μm), with mixture 23% acetonitrile and 77% water as mobile phase at a rate of 1.2 mL／min and 25 ℃， the wavelength for the measurement w as 230 nm.　The results show that the content of the four diterpenoids in Rabdosia e xcisa are different in different growth periods. Kamebakaurin (Ⅰ) and excisanin A (Ⅱ) could reach the highest content respectively in the first ten days of July; Rabdokunmin C (Ⅲ) has a little variation from the begin of June to the beg in of August, then, the content would decrease; Kamebanin (Ⅳ) could reach the highest content in the middle ten days of June, the content would decrease then. The total content of the four diterpenoids is the highest in the first ten days of July.

Key words: Rabdosia excisa (Maxim.) Hara, diterpenoids, RP-HPLC, variation