Abstract: Based on the data from 22 acid rain monitoring stations from 2004 to 2008 in Liaoning province, the spatial-temporal distribution characteristics of acid rain were analyzed. The results show that the annual average of pH value ranges from 5.49 to 6.62 with a decreasing tendency. However, the acidity is an increasing tendency year by year. The acid rain occurs mainly in Dalian, Dandong, Xingcheng and Benxi country. The highest acidity appears in Dalian, while the lowest is in Jianping in the west of Liaoning province. The acid rain is of obvious seasonal variation in Liaoning province, and pH value is the highest in summer and the lowest in spring. Moreover, the occurrence frequency of the acid rain is the highest in autumn and the lowest in spring.