This paper presents the trend analysis of precipitation acidity over China based on the records of pH value of precipitation obtained from Acid Rain Monitoring Network operated by China Meteorological Administration, with an emphasis on Beijing-Tianjin region. The analysis shows that the area of precipitation acidification, with low pH value and high frequency of acid rain, extends significantly over China in recent years, and that especially the acidity of precipitation in Beijing-Tianjin area has increased significantly since 2000. This trend of increasing acidity of the precipitation within Beijing-Tianjin region corresponds to the decline of the concentrations of airborne particles in Beijing and Tianjin, as a result of the pollutant/particle abatement effort toward 2008 Olympic game in Beijing, suggesting a possible linkage between the trend of precipitation acidity and the particle control measure. This linkage implied the sensitive response of the precipitation acidity on the control of particulate pollutants in a regional scale.