To establish a LC-MS method for the simultaneous determination of evodiamine and tutaecarpine in water extracts of Evodia rutaecarpaMethods：A Welch Materials Xtimate-C18 (2.1 mm×150 mm，3 μm) was used . The mobile phase consisting of a mixture of methanol and 10 mmol/L ammonium acetate(85：15) was delivered at a flow-rate of 0.2 mL/min. The column temperature was maintained at 30 ℃. The mass spectrometer was operated under the positive ion mode. Atomization pressure(N2) was 40 psi, voltage was 4000v and temperature was 100 ℃.The drying gas (N2) flow was 10 L/min, the drying gas temperature was 350 ℃.Results：The linear ranges were 2.02～504 ng/mL (r=0.9992) and 1.97～493.33 ng/mL (r=0.9999) for evodiamine and rutaecarpine. The method extraction recoveries of evodiamine and rutaecarpine were 87.8％~97.04% and 86.35％~98.22% respectively. The intra– and inter –day RSD were also lower than 10%.Conclusion：The method is simple, reliable and sensitive. It can be used for the pharmacokinetics research of water extracts of Evodia rutaecarpa.