Abstract: Optical measurement are often affected by low signal-to-noise ratios (SNR), resulting in larger measurement uncertainty. Measurement of the bidirectional reflectance distribution function (BRDF) in the near-infrared is particularly vulnerable to environmental interference due to weak infrared signals. The signal-to-noise ratio problem of optical measurement systems generally arises from detection systems. For infrared measurement systems, choppers and lock-in amplifiers are often used for weak signal measurement, but noise problems are also introduced at the same time. Therefore, this article focuses on the SNR of BRDF measurement in the near-infrared, aiming at the detector, chopper and lock-in amplifier, analyzing the source of noise, and proposing suppression methods and optimization measures to improve the signal-to-noise ratio. The optimized measurement system has improved anti-noise ability compared with that before optimization, and the repeatability has been improved from 2.1% to 1.6%.