A method was developed for the simultaneous determination of carbon monoxide，carbon dioxide and three light hydrocarbons i.e.methane，ethylene and acetylene in air by gas chromatography.The GC system consisted of auto-injection，one ten-port valve together with a six port valve and one ten-port valve in series with a four-port valve.Sample injection，column isolation and column back-flushing were realized in this way mentioned.An HP-PLOT Q open tubular capillary column was employed for the separation of the five gases followed by thermal conductivity detection.After the separation was completed，carbon monoxide and carbon dioxide were converted into methane with the use of a nickel-based methanizer for the detection by flame ionization.Separation of all the target analytes was achieved in one single analysis within 9 min.Carbon monoxide，methane，carbon dioxide，ethylene and acetylene were found to be linear over the ranges of 3.3-4 990.0，3.3-5 010.0，6.6-4 990.0，4.2-5 080.0,3.9-5 030.0 μmol/mol，respectively.The correlation coefficients were not less than 0.997 with the detection limits of 1.0-2.0 μmol/mol.Reproducibility of two levels，namely std1 and std2 were found to be not more than 3.5%(n= 5).This method was simple，accurate and maneuverable.