提出了一种利用窄线宽激光作为测量光源,对光学谐振腔自由光谱区、腔内共振激光波长进行精密测量而得到光学谐振腔腔长的方法。对光学谐振腔腔长的测量理论进行了严格推导,通过理论模拟对测量条件及结果进行了分析讨论。以自行研制的线宽为1.9Hz、频率不稳定度为1.7×10-14 s-1、中心波长为1550nm的窄线宽激光作为光源,对长度约100mm的光学谐振腔腔长进行了精密测量。对光学谐振腔自由光谱区进行测量,得到其腔长为0.10024407m、精度为22nm;对光学谐振腔腔内共振激光波长进行测量,得到其腔长为0.1002440884m、精度为0.21nm,精度相对提高了2个量级。提出的方法有望促进基础物理研究、材料的物理属性精密测量及光纤传感等领域的发展。 A method of using the narrow linewidth laser as the measurement light source to obtain the cavity length of the optical resonant cavity through precise measurement of the free spectral range of the optical resonant cavity and the cavity resonant laser wavelength is proposed. The measurement theory of optical cavity length is strictly deduced, and the measurement conditions and results are analyzed and discussed through theoretical simulation. The length of the optical cavity with a length of about 100 mm was measured with a self-designed narrow-linewidth laser with a linewidth of 1.9 Hz, a frequency instability of 1.7 × 10-14 s-1 and a center wavelength of 1550 nm . The cavity length of the optical resonator is 0.10024407m and the accuracy is 22nm. The wavelength of resonant laser cavity in the optical cavity is measured. The cavity length is 0.1002440884m, the accuracy is 0.21nm, and the accuracy is improved 2 orders of magnitude. The proposed method is expected to promote the basic physics research, the physical properties of materials, precision measurement and optical fiber sensing and other fields.