For obtaining high power 9.3 μm laser, high power pulse CO2 laser is used to select band. Band selection is done by resonator mirror filming. By controlling the transmittance or reflectivity of different wavelengths, 9.3 μm laser is got both in stable resonators and unstable resonators. With the same operation parameters, the energy of 9.3 μm laser is 95% of 10.6 μm in stable resonators, while 93% in unstable resonators. Both in two different resonators, the thermo-sensitive paper colors by 9.3 μm laser are evidently different from those by 10.6 μm laser. Experimental results show that the resonator mirror filming method can lead 9.3 μm laser output both in stable and unstable resonators, and the energy is changing slightly. The thermosensitive paper displays the 9.3 μm laser has stronger impact erosion than the 10.6 μm laser.