Accurate diffusion was used to get low concentrations samples, and then the samples were detected by UV photoionization high-field asymmetric ion Mobility spectrometry ( UV-FAIMS ) . The samples were chemical warfare agent simulants ( CWAS) vapor:dimethyl methylphosphonate ( DMMP ) , dimethyl sulfoxide ( DMSO) , tributyl phosphate ( TBP ) and dimethyl sulfoxide ( DMF) . The results of FAIMS spectra data were analyzed by separation of spectra at different dispersion voltage ( DV ) and compensation voltage ( CV ) . A two-dimensional spectrum of α2 and α4 of CWAS was established. It was shown that FAIMS could identify CWAS well and have a good sensitivity. Take DMMP as a example, the detection limit was better than 0. 55 μg/L.