Cavity-enhanced/ring-down spectroscopy is one of the most widely used spectroscopy techniques for the high sensitivity, real time, in-situ measurement of aerosol extinction coefficient. The nature suspended state of aerosol is not changed during the measurement. After nearly 30 years development, the techniques are well developed. The instrument based on cavity-enhanced/ring-down method was served as a standard instrument for the intercomparisons with other optical measurement instruments. The development and the application of cavity-enhanced/ring-down spectroscopy for aerosol extinction measurement were briefly reviewed.