A new method for simultaneous determination of ephedrine, pseudoephedrine and methylephedrine in the decoction of Ephedrae Herba by normal phase high-performance liquid chromatography is reported. By using silica gel column and the mixture of n-hexane, ethanol and ammonia (125 : 75 : 1) as a mobile phase, each alkaloid was well separated within 10 min. Optimal wavelength for detection was found to be 220 nm by three dimensional observation. Reproduceble peak area calculation was achieved by the peak smoothing technique.