The combustion-chamber’s composition、small-signal gain distribution along flow direction and laser’s power and specific power of the combustion-driven gas-dynamic CO2 laser with toluene、benzene、kerosene and alcohol separately combustion driven were numerically simulated. The four different conditions were compared and the results will be referential to CO2 laser’s study. The results indicated toluene is an optimum fuel of the four gas-dynamic CO2 laser’s fuels.