根据以前双纵模绝对距离测量中合成波长过大导致误差较大的缺点，设计了一种新型多波长绝对距离干涉测量系统。采用633 nm双纵模He-Ne激光器中的一个纵模和629 nm波长的He-Ne激光组成117 μm合成波长，使用双外差干涉技术对距离改变进行精密测量。静态稳定度和动态测量实验表明，由于采用了较小的合成波长，系统的测量不确定度可以达到3.8×10-6L+57 nm，在 500 mm的距离上不确定度小于2 μm。最后从合成波长不确定性的角度，对干涉系统中的误差作了分析。该系统如能与双纵模拍波测量作衔接则可实现对被测距离由粗至精的测量。

To overcome the defects of large error in two-longitudinal-mode wavelengths interferometer for absolute distance measurement, a new kind of multi-wavelength absolute distance interferometer is introduced. A double-mode 633 nm He-Ne laser and a 629 nm He-Ne laser are employed to generate 117 μm synthetic wavelength, with which distance with high precision is measured by using the double heterodyne interferometric technique. The static and dynamic experiments show that due to the shorter synthetic wavelength, the uncertainty can reaches 3.8×10-6L+57 nm and the error is 2 μm within 500 mm. From the uncertainty of synthetic wavelength, the error of the new interferometer is also discussed. The interferometer could measure distance with high precision if coupled with two-longitudinal-mode beat measurement system.