Objective:To establish an HPLC method for the determination of Cinnamic acid、Cinnamaldehyde in Guzhi Decoction. Methods:Defferent decoction were preparded and analyzed by L16(215)orthogonal design,the contents of the Cinnamic acid and Cinnamaldehyde in each decoction was determined by HPLC.Results:Different compatibilities have significantly on content of Cinnamic acid and Cinnamald.Conclusions The method is simple,effective,sensitive and feasible.