Abstract: The liquid chromatography tandem triple quadrupole mass spectrometry (LC-MS/MS) is widely used in environmental analysis, food safety, drug metabolism research, biomedicine and other fields. It is mainly used for the detection of trace targets in complex sample matrix, which is suitable for the qualitative of small molecular organic compounds and the quantitative of trace compounds. The main detection mode is multiple reaction monitoring (MRM). It has excellent detection sensitivity and quantitative function in MRM mode by abundance ratio of qualitative ion pair to qualitative and peak response of quantitative ion pair to quantitative. Reasonable standard use and maintenance of the LC-MS/MS is the basic requirement to ensure accurate and effective test data and sustainable normal operation of the instrument, and is also an important measure to reduce the maintenance cost of the instrument. The operating principle, power-on, power-off, tune about the LC-MS/MS of Agilent were described, and the common faults and countermeasures, as well as the contents of daily maintenance were discussed in order to provide a reference for the rational and standardized use of the instrument.