在空天探索领域，空间引力波探测是当前国际研究热点，核心技术是测量相距数百万千米的两测试质量间的平动转动等多个自由度，探测灵敏度需要在1 mHz~1 Hz频段达到~1 pm/Hz^1/2以及~1 nrad/Hz^1/2水平。目前，激光干涉是实现如此远距离的两个物体之间多自由度测量的最精密的手段，本文介绍了面向空间引力波探测的激光外差多自由度超精密测量技术，概述了其光路结构、测量原理、相位信号处理方法，回顾了近三十年国内外相关研究进展，并分析了空间引力波探测中外差干涉测量的噪声源作用机制以及相关研究进展。最后，对激光外差干涉多自由度超精密测量技术的发展趋势和前景作了展望。

Space gravitational-wave detection is currently an international hotspot. The core technology is to measure the multi-degree-of-freedom motions between two test masses with a distance of few million kilometers. The test sensitivity needs to reach the level of ~1 pm/Hz^1/2 and ~1 nrad/Hz^1/2 within the frequency band of 1 mHz and 1 Hz. At present, laser interferometer is one of the most precise methods to achieve ultra-precision displacement measurement. In this paper, we introduce the ultra-precision multi-degree-of-freedom measurement using laser heterodyne interferometry for space gravitational-wave detection. The optical design, measurement principle, phase demodulation, and relative research progress at home and abroad are introduced. We also analyze the main noises of laser heterodyne interferometry in space gravitational-wave detection, and the current research of these noise sources are also introduced. Finally, the development trend and prospect of laser heterodyne interferometry for ultra-precision multi-degree-of-freedom measurement are forecasted.