The invention provides a kit for detection with a tandem mass spectrometry. The kit comprises an extracting solution and a mobile phase, and optionally comprises one or more of a quality control standard substance, an isotope standard substance of a target analyte and a derivatization reagent, wherein the extracting solution is a methanol aqueous solution with the concentration being 85%-95% by volume, and the mobile phase is a mixture containing water, acetonitrile and pentafluoropropionic acid with the volume ratio being (70-90): (15-25): (0.15-0.25) of . The invention also provides a usagemethod and an application of the kit.