为实现在高功率激光装置中对平面反射镜反射率的高精度测量,提出了将双光束分光光度法与VW测量法相结合,利用扩束后的测量光束测量被测元件的反射率。推导了计算公式,搭建了测量光束口径为50mm的检测系统,通过对标准吸收玻璃吸收值的测试验证了系统对光束能量测试的准确性。利用该系统对高功率激光装置使用的反射镜的反射率进行了测量,并将其测量结果与用lambda900分光光度计测量的结果进行了比对。结果表明:该方法的测量精度优于0.1%。 In order to achieve the high-accuracy measurement of reflectivity of flat mirror in high-power laser device, a new method is proposed, which combines the two-beam spectrophotometry and the VW measurement method to measure the reflectivity of the device under test. The calculation formula was deduced and a measuring system of measuring beam diameter of 50mm was set up. The accuracy of the system testing the beam energy was verified by testing the absorption value of the standard absorption glass. The system was used to measure the reflectivity of mirrors used in high power laser devices and the results were compared with those measured with a lambda 900 spectrophotometer. The results show that the accuracy of this method is better than 0.1%.