Based on the acid precipitation monitoring data from 2003 to 2006 at Weifang Acid Monitoring Station, analyzed are the seasonal variation characteristics of acid precipitation and the relationship between acid precipitation and meteorological conditions. The statistics show that in 186 precipitation samples, there are 39 acid samples with pH>5.6 (21.0%), 147 samples with pH≥5.6 (79.0%). The occurrence frequency of acid precipitation is the highest in autumn, and lower in spring; the acid precipitation occurs more frequently during the night, and the nonacid precipitation occurs usually in the daytime; the acid substances float at middle and upper levels of the atmospheric boundary layer, and the alkali substances at the middle and lower levels. It is concluded that the occurrence of acid precipitation has close relationship with the density of air pollutants, the height of the atmospheric mixed layer, wind direction and speed, precipitation, and the fog.