A synthetic-wave absolute-distance interferometry system is proposed to achieve high-accuracy absolute-distance measurements. In this system, the light source is a quadrature-demodulated Pound-Drever-Hall frequency-stabilized two-cavity dual-frequency Nd∶YAG laser (TCDFL) with a significant frequency difference. A Mach-Zehnder interferometry structure is employed, and a synthetic-wave absolute-distance heterodyne interferometric system is designed; hence, two heterodyne interference signals with the same frequency can be obtained. The phase-difference of both heterodyne interference signals is measured to determine the fractional order of the synthetic-wave interference fringes. In addition, the integer order of the synthetic-wave interference fringes can be uniquely determined by preliminarily estimating the measured distance. Thus, absolute-distance measurements can be achieved. An experimental system of synthetic-wavelength calibration and absolute-distance interferometric measurement is established using the diode-pumped orthogonally and linearly polarized TCDFL with a frequency-difference of 24 GHz at 1064 nm. The experimental results show that the synthetic-wavelength in the air is 12.4614 mm with a standard deviation of 0.13 μm. A repeated measurement average of 899.3851 mm is obtained at a measured absolute-distance of 900 mm. Correspondingly, the standard deviation and measurement uncertainty are estimated to be 1.36 μm and 4.08 μm, respectively. This experimental study lays a solid foundation for future research and development of high-precision absolute-distance interferometers.