Abstract: GC-MS combined with summa canister sampling was applied to the determination of toxic gases in air of closed environment. The 8 toxic gases included styrene, chlorobenzene, carbon disulfide, trichloroethane, trichloroethylene, tetrachlorothylene, naphthalene and hexane. The gas components were collected in a summa canisters and preconcentrated with a preconcentrator. The gas mixture was seperated on a DB-5 capillary column, and then was analyzed by MS. The conditions of column type, column temperature, preconcentrated temperature and injection volume were optimized. The linearity ranges of 8 compounds were all 0.002 0-0.050 0 mg·m-3, with detection limits (3S/N) in the range of 0.2-0.4 μg·m-3. The proposed method was used to determine toxic gases in air of closed environment, giving recovery rates obtained by standard addition method in the range of 88.6%-97.1% and RSDs (n=6) in the range of 1.4%-9.4%.