Abstract: The compositional analysis of coal-bed methane is very important for its exploitation and utilization. The gas chromatography is used for measuring the compositions of the coal-bed methane, the standard gas is used for its qualitative analysis and the external standard method is used for its quantitative analysis. A gas chromatographic instrument having two columns and a single gas way is used so as that the compositions of the coal-bed methane can be analyzed on its two columns and the analysis of the main compositions of the coal-bed methane can be implemented by one sample injection. Relevant experimental research was carried out according to the influence factors including the chromatographic columm temperature, the injected gas temperature, the carrier gas flowrate and so on and investigation was also made on the repeatability of this measuring method. The research results showed that this method had the advantages of easy operation, accurate result and short analysis time.