The invention relates to a combined interference chamber for chemical laser device wavelength choice output. A stable chamber structure is adopted in the combined interference chamber which comprisesa recessed surface reflecting mirror, a 45 degree beam splitting sheet and two plane reflecting mirrors. The 45 degree beam splitting sheet and the two plane reflecting mirrors form an interference sub-chamber, and reflecting films having different reflectivity for laser light with different wavelengths are respectively plated on reflecting planes of the recessed surface reflector and the plane reflecting mirrors. Via control over reflectivity parameters of optical elements in a laser resonant cavity, wavelengths of a laser device can be chosen roughly; interference effects are used for closely adjacent wavelengths can be chosen in a careful way via adjustment of parameters such as a length of the interference sub-chamber, a beam splitting ratio of a beam splitting sheet and the like; thelaser device is enabled to output laser light with any single wavelength.