Adstolochic acids (AAs) are the main components in Aristolochia plants, which are related to a severe kidney disease called Chinese herbs nephropathy (CHN).In this study, a capillary electrophoresis-electrospray ionization mass spectrometry (CE-MS) method was proposed to separate AA-Ⅰ and AA-Ⅱ(Fig.1).A background solution composed of ammonium acetate (pH =4.6) was proved to be suitable to the CE-MS analysis on a capillary with effective length of 78.5 cm.Some parameters such as the capillary position, the composition and flow rate of the sheath liquid, capillary length were optimized in this work.