This standard specifies the method for the determination of melatonin in health food packaged in capsules or tablets with melatonin as the active ingredient. This standard applies to the determination of melatonin in health food packaged in capsules or tablets with melatonin as the active ingredient. The detection limit of the first method of this standard, HPLC-UV detection method, is 0.5ng; when the sampling volume is 0.5g, the detection concentration is 0.07mg/kg. The detection limit of the second high-performance liquid chromatography-fluorescence method is 30pg, and the linear range is 0.05ng~0.50ng.