Abstract: Volatile organic compounds（VOCs）in air do great harm to human health. This paper reviews the progress in research on the on-line monitoring techniques for volatile organic compounds （VOCs）in recent years at home and abroad. Some on-line monitoring techniques，including membrane extraction gas chromatography，proton-transfer-reaction mass spectroscopy，time-of-flight mass spectrometry，Fourier transform infrared spectroscopy and laser spectroscopy are introduced and compared. The advantages and shortages of tunable diode laser absorption spectrometry are discussed，and the prospect of its application is also presented.