This paper presents the basic principle and design method of the cruor measurement system with photometry. Meanwhile the hardware structure and data processing method of the system are also presented. The selection of different monochromatic lights increases the specificity of the tests. The Percentage Detection Method reduces the impacts of the special samples on the results. The effect of stray light is eliminated by taking two fairly close measurements of the transmitted light during the absorbance measurement. Thereby the tests can be more accurate.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.