It is the key of absolute distance interferometry to establish a synthetic-wave measuring chain. This paper gives a general formula of synthetic-wavelength and a conventional measuring equation set for each stage of synthetic wave, and introduces two-stage synthetic hierarchy produced by 3.3922um and3.3912um dual-line He-Ne laser, as well as the related experimental results. On the basis of the hieraehy, this paper puts forward two interference measuring approaches. The discussion and analysis show that these two interfering system can be suitable to measurement of distance ranging from several meters to 100 meters, with an accuracy better than 1×(10-6~10-7).