Based on the monthly precipitation data in the Pearl River Delta Area from 1980 to 2010, a Mann-Kendall trend test was made in this paper. The results show that the rainfall in the Pearl River Delta Area has a significant declining trend from February to April and a significant decreasing trend from June to September. This paper analyzed the causes of this trend from the perspective of aerosol. The precipitation, which is from February to April, has different rainfall patterns, compared to the precipitation from June to September, this paper hypothesized the increase of aerosol substance, to some extent, inhibited the formation of frontal gland precipitation from February to April and may also has some influence in the typhoon rain from June to September. There is also an explanation of the hypothesis.