Abstract: High resolution gas chromatography-quadrupole time-of-flight mass spectrometry(GC-QTOF) can be acquired in single mode time-of-flight mass spectrometry(TOF), with the use of accurate mass number of collected ions to analyze unknown compound, and carry out structure identification, which are mainly based on the use of the National Institute of Standards and Technology(NIST) library of the low resolution and personal compound database and library (PCDL) of high resolution. GC-QTOF also can analyze unknown compounds by QTOF fragment ions, which are mainly based on the use of the molecular structure of software (MSC) and Chemspiders database (web) and so on. Besides to operate the instrument correctly with regular maintains, and make the instrument in good working condition, in order to get the accuracy and effectiveness of the test data. The use and maintenance of GC-QTOF from Agilent is introduced.