Abstract: In order to obtain 9.3μm laser output, the small signal gain coefficients of 5 kinds of CO₂ isotopes were compared. After theoretical analysis and experimental verification, isotope gas ¹²C¹⁸O₂ was chosen as the working medium and laser output of 9.3μm was obtained. After the optimization of the working pressure of the laser, the maximum 96W power output was obtained under 10.00kPa working pressure. The results show that high power laser output can be obtained when the central wavelength of ¹²C¹⁸O₂ is near 9.3μm. The study is helpful to localize 9.3μm CO₂ laser and improve the localization rate of core components.