Using STM32 microprocessor, a non-invasive skin cholesterol detection system based on absorption spectroscopy was designed. The relative cholesterol content of human skin was indirectly obtained by absorption spectrum information of colored products which was detected by micro-spectrometer. The system was designed with a high-precision adjustable LED constant current source, and the fluctuation range of LED light intensity is controlled within ±1%. A liquid limit device with a simple structure, a small amount of reagents, and no need for an exact detection reagent volume was also designed to achieve accurate measurement of the measured liquid concentration. By detecting the concentration of CuSO4 solution, the accuracy of the system for quantitative detection of different concentrations of solution was verified. Using this system to detect the skin cholesterol of patients with atherosclerotic disease and control population, the test results have statistically significant differences, which preliminarily verifies that system can be used for human skin cholesterol detection.