Finite difference technology and compressible scaling method (CSM) are used to the simulation of the combustion driven CW DF chemical lasers. Different fuels (H 2 and C 2H 4) and different diluents (He and N 2) are calculated. The components of mixing gas in the combustor, small signal gain, line intensity distribution of optical cavity, output power and chemical efficiency of lasing are given. The results showed that: the lasing zone of the DF chemical laser is longer and much easy to adjust when C2H4 is used as fuel and He as diluent, the chemical efficiency is higher, and the line intensity distribution is more converged.