To better understand soil-accelerated acidification process and its amelioration countermeasures, the effects of planting peanut and applying urea and several kinds of organic materials (rice straw, Chinese milk vetch, pig manure) on soil acidity were studied by pot experiment between 2007 and 2008. The results indicated that, compared with the soil in the treatments without planting peanut, soil pH in the treatments with planting peanuts decreased by 0.06 - 0.28 one year later and by 0.08 - 0.27 two years later, meanwhile the contents of soil exchangeable Al increased by 7.69% - 72.94% and 8.49% - 46.20%, respectively. Applying urea increased the yield of peanuts but accelerated soil acidification process. Compared with the soil in the treatments with low rate of urea, soil pH decreased by 0.02 - 0.10 one year later and by 0.01 - 0.16 two years later after applying high rate of urea. Organic materials had various ameliorating effects on soil acidity, with the order of pig manure＞rice straw＞Chinese milk vetch. Soil pH increased but the content of soil exchangeable Al decreased with the applying rate. Among the organic materials, pig manure increased peanut pod yield significantly, and the dry weight of peanut stalk increased by 11.12% - 59.28%, and the dry weight of peanut pod increased by 12.42% - 68.20% in two years, compared with treatments only with chemical fertilizers. Chinese milk vetch also slightly increased peanut yield but rice straw had an insignificant effect on peanut yield.