Abstract: Gas chromatography was applied to the determination of oxygen,nitrogen,methane and carbon monoxide in gaseous phase of mainstream smoke of cigarettes.Samples were collected according to the trade standard of tobacco industry.Standard gases of O2,N2,CH4 and CO were used and definite amounts of the gases were introduced into the instrument in preparation of standard curves.Precision of the sample collection and stability of the intrument in operation were tested,and satisfactory results were obtained.Linear relationships between values of peak area and mass concentration of the 4 gases were obtained in the ranges of 52-520 mg·L-1 (for O2),276-736 mg·L-1 (for N2),3.4-11.2 mg·L-1 (for CH4) and 18-65 mg·L-1 (for CO) when 100 μL of the sample was introduced.Mixture of definite amounts of the standard gases were prepared and used for testing precision and accuracy of the proposed method,giving values of relative deviation (absolute value) (n=6) less than 5%,and values of RSD′s (n=6) of the analytical results less than 2.5%.