Abstract: A method of IC for determination of L-carnitine in slimming diet was proposed. The sample was extracted with ultrapure water for 30 min at 30 ℃, after centrifugation, the supernatant was purified by passing through OnGuard II RP column. IonPac CS17 column was used for separation with 5 mmol·L-1 methylsulfonic acid solution as eluant. Non-inhibitory conductivity detection was adopted in the determination. Linear relationship between values of peak area and mass concentration of L-carnitine was obtained in the range of 10-1 000 mg·L-1, with detection limit (3S/N) of 1 mg·g-1. Using 2 samples of slimming diet as matrixes, test for recovery was made by standard addition method, giving values of recovery and RSD′s (n=5) in ranges of 95.4%-101% and 0.9%-6.6% respectively.