A high-performance liquid chromatography-mass spectrometric method was developed for the determination of L-carnitine in infant formula milk powder.After pretreatment procedure，the sample was separated on a C4 （4.6 mm×250 mm，5 μm） column using methanol-water （10∶90） as mobile phase with a flow rate of 1.0 mL?min-1，a column temperature of 25 ℃ and injection volume of 10 μL.The split ratio of post column was 1∶3.The target compound was detected under multiple reaction monitoring（MRM） mode with positive ion using m/z 162.2→103.1 as the quantitation ions.Each analysis was completed within 10 min.A good linear calibration for L-carnitine was obtained in the range of 0.40-10.0 mg?L-1 with a correlation coefficient of 0.999 3.The spiked recoveries were in the range of 87%-106%.The limit of detection（S/N=3） and limit of quantitation（S/N=10） of L-carnitine were 39.0 ng and 116.9 ng，respectively.The proposed method was simple，sensitive and reproducible，and was suitable for the determination of L-carnitine in infant formula food.