Abstract: It’s necessary to establish a high-precision analytical method of gas chromatography for achieving the rapid detection of trace impurity components in process gas of fusion reactors. The separation of impurities relied on capillary column of molecular sieve and PLOT-Q under different column temperature and the flow rate of carrier gas, respectively, with the impurity concentrations of 1, 10 and 100 ppm in standard gas and the application of discharge ionization detector (DID) in high purity helium. The studies show that the separation of H₂, O₂, N₂, CH₄ and CO with the capillary column of molecular sieve achieves in 160 s with high column efficiency and good repeatability, while the column temperature is 40 ℃ and the flow rate is 15 mL/min to 20 mL/min, the resolution between H₂ and O₂ is more than 1.5, which can achieve complete separation. The experiment conditions with column temperature of 40 ℃ and the flow rate of 20 mL/min fit to separate CO₂ with the column of PLOT-Q.