Objective: The pupose of this article study the effects of gypsum on the contents of ephedrine

pseudoephedrine

amygdalin

liquiritin and glycyrrhizic acid in Maxingshigan decoction. Method: HPLC method was employed to determine the five components in both decoctions with and without gypsum. The Agilent ZORBAX SB-Aq C18 column (4.6 mm×250 mm

5 μm) maintained at 30 ℃ with a gradient mobile phase system consisting of ACN-0.1% phosphoric acid solution was used for sample analysis. The wavelength of the UV detector was set at 207 nm for ephedrine

pseudoephedrine and amygdalin

while 237 nm for liquiritin and glycyrrhizic acid with a flow rate of 1.0 mL·min-1. Result: The concentration of ephedrine

pseudoephedrine

amygdalin

liquiritin and glycyrrhizic acid were 197.80

64.32

448.05

56.81

119.76 mg·L-1 in traditional Maxingshigan decoction with gypsum while in the case of gypsum-free

the concentrations of the five componts were 183.08

54.57

368.79

50.34

143.92 mg·L-1 in Maxingshigan decoction without gypsum

respectively. Conclusion: Gypsum had influence on the contents of other constituents. It could significantly increase the contents of ephedrine

pseudoephedrine

amygdalin

liquiritin but reduce the content of glycyrrhizic acid.