Abstract: In order to measure aerosol extinction coefficients with higher sensitivity, a system for measuring aerosol extinction coefficients was set up based on high-reflectivity cavity mirrors and pulse cavity ring-down technology. The actual atmosphere under different conditions was measured. The experimental results were analyzed and studied, and compared with the research results at home and abroad. The results of the experiment show that cavity ring-down time is greater than 40s, stability is better than 0.3% and detection sensitivity is greater than 1.810-7m-1. Cavity mirrors with high reflectivity and pulse cavity ring-down technology are quite feasible in development of detection systems of aerosol extinction coefficients with high sensitivity.