Abstract: The chemical speciation of ambient VOCs in Beijing city was analyzed by using the method of pre-concentration-GC-MS. A total of 108 VOCs species were detected. The average mass concentration of VOCs in Beijing was (163.7±39.0) μg/m~3. The major components were alkanes, aromatics, alkenes, halogen alkanes, halogen alkenes and halogen aromatics which accounted for 33%, 21%, 16%, 20%, 9% and 1% respectively. The more important problem was that 54 species of toxic VOCs were detected in the ambient air of Beijing city, the main compounds were aromatics and halogen hydrocarbons, namely benzene, toluene, propylene, 1,3-butadiene, chloroethylene and 1,2-dichloroethane.