ETHNOPHARMACOLOGICAL RELEVANCE: Alismatis rhizoma (AR), a Traditional Chinese Medicine with lipid-regulating properties, is usually used to treat hyperlipidemia. Lysophosphatidylcholines (Lyso PCs) play a crucial role in lipid metabolism disorders. In this study, the triterpene fraction purified from boiling water extract of AR was evaluated for its lipid lowering activity using mice with high-fat diet (HFD) induced hyperlipidemia. The metabolic changes of individual Lyso PCs treated with the triterpene fraction were detected by ultra-high performance liquid chromatography-triple quadrupole-linear ion trap mass spectrometer (UHPLC-QTRAP-MS/MS). MATERIALS AND METHODS: HFD induced hyperlipidemia mice were administrated with triterpene and non-triterpene fractions at doses of 180, 360 and 720 mg/kg body weight/day for 4 weeks, respectively. Total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and atherogenic Index (AI) in mice serum were measured. The chemical components in the lipid-lowering fraction were characterized by ultra-high performance liquid chromatography-quadrupole time of flight tandem mass spectrometry (UHPLC-QTOF-MS/MS). The changes of Lyso PC in the serum of mice treated with the lipid-lowering fraction were quantified by UHPLC-QTRAP-MS/MS. RESULTS: A total of 18 alisol derivatives were identified in the triterpene fraction. The hyperlipidemia mice treated with the triterpene fraction showed a significant decrease in serum TC, LDL-C and AI after continuous consumption of HFD for 4 weeks. The results also showed that 27 serum Lyso PCs in mice fed with HFD were down-regulated, and 19 were up-regulated. The abnormal serum level of Lyso PCs associated with hyperlipidemia was intervened by the alisol derivatives, with increase of unsaturated Lyso PCs and decrease of saturated ones. CONCLUSIONS: The study demonstrated for the first time that triterpenes from the AR extract can lower serum lipid level in HFD induced hyperlipidemia mice. These metabolism changes of Lyso PCs could further improve our understanding of the potential mechanism of lipid lowering effect of AR.