The results of experimental studies on the compatible using of Fructus Evodiae with Rhizoma Coptidis show that in the decoction of the two drugs there is an additive property for the chemical constituents and no new chemical substances were found. But the decocting rate of berberine, the main constituent of Rhizoma Coptidis, decreases by 37.0% after decocting with Fructus Evodiae.