An electron beam pumped rare gas excimer lamp（EBEL） was utilized to emit the intensive vacuum ultraviolet（VUV） radiation at 126 nm for soft single photon ionization（SPI） of polycyclic aromatic hydrocarbons（PAHs） in a soil sample.The VUV light source was coupled to a compact and mobile time-of-flight mass spectrometer（TOF MS） for the on-line detection of PAHs.The PAH desorption gases from soil sample were introduced into the mass using direct sample introduction with a cappillary.The effects of moderate desorption temperatures and desorption time on 16 PAHs were discussed,and the influences of the ionization efficiency of the single photon ionization on limits of detection were also considered.The quantitative analysis was carried out by measuring the mixture of a standard gas,and the limits for detection for 16 PAHs in the environmental soil were found to be at a μg/mL level.