Abstract: A review on the principles and characteristic of soft ionization mass spectrometry, including chemical ionization, electrospray ionization, atmospheric pressure chemical ionization, laser desorption ionization and single-photon ionization, was presented, prospecting especially for their application to the field of tobacco chemistry, such as the analysis of harmful ingredients in tobacco and tobacco smoke, real-time and online determination of cigarette smoke, separation and identification of potential aroma substances and residual pesticide, and so on (54 ref. cited).