Precipitation is the major but more variable factor of climate change, light rain is more sensitive to temperature variation and aerosol. By using the daily data of precipitation, visibility and relative humidity observed at 46 weather stations over Sichuan Basin during 1973─2010, we analyzed the long term trend of light rain (0~1 mm) over Sichuan basin, and further discussed the possible relationship between light rain and aerosol variation. The results showed that, (1) precipitation contributed by light rain days exhibits a decrease trend over Sichuan Basin. The annual light rain days is 72.2 day, The decreasing rate of light rain days is-3.3 d/10 a, especially at west and north Sichuan Basin. (2) The variations of Aerosol optical extinct coefficients (AEC) are significantly positive-correlated with light rain days over most area of Sichuan basin, which is especially apparent in the areas with low visibility. (3) The variation factor of light rain days (R_0) decrease 7% during the study years, while aerosol burden (represented by visibility in the study) increase, which implied that the reduction of light rain is probably related to the variation of aerosol, i.e. increasing of aerosol suppress light rain over Sichuan Basin.