Ultra-fine particulate matter (PM_0.1) emission from automobile exhaust and its aging process in the atmosphere have a significant impact on human health and environmental climate. In this work, the optical absorption coefficients of PM_0.1 in the exhaust of 18 automobile under no-load idle state and after 4 hours and 14 hours of light aging were researched with photoacoustic spectroscopy at 1064 nm. The results showed that the optical absorption coefficient of PM_0.1 in vehicle exhaust decreases obviously after the implementation of National V standard in China, which is positively correlated with engine displacement, service life and weight and the optical absorption coefficient of PM_0.1 increased first and then decreased during light aging. This work provides an experimental basis and data support for further understanding of the light absorption characteristics and environmental behavior of PM_0.1 in automobile exhaust.