A RP-HPLC method for the determination of TTX in the liver of Fugu vermicularis was established.The operating conditions were Hpersil BDS C18(5?m,250mm*(4.6mm) i.d),mobile phase of phosphate with Heptane-1-sulfonic acid sodium salt as an ion-pair reagent and diode array detector.The linear relationship of calibration curve was good in the range of 2.5～250?g?mL~(-1)for TTX.The detection limit was 40ng,and the relative standard deviation was 2.24%～2.68%,and the recoveries ware 79.17%～84.38%,the intra-day precision was 1.782%(n=5),and the inter-day precision was 4.554%(n=5).This method was simple,accurate and sensitive.