[Objective] Soil pH is a key index for quality evaluation of cultivated lands. So this paper explored temporal and spatial changes in soil pH of farmlands in Shandong Province in the past 30 years, analyzed overall situation of and dynamic changes in soil acidification, and discussed natural and human-driven factors affecting soil acidification, so as to provide certain scientific references for prevention and control of soil acidification in Shandong Province. [Method] Based on the soil pH data cited from the "Second Provincial Soil Survey in 1984' and the "Provincial Arable Land Fertility Evaluation (PALFE) in 2015", the soils of the province were sorted into seven grades, i.e. I. Highly acidified soil (pH ≤ 4.5), II. moderately acidified soil (4.58.5), in line with the criteria for soil grading in terms of soil pH (Cultivated Land of Shandong) and in light of the reality of the province. The Kriging method and some other statistical methods commonly used in geostatistics were adopted to analyze the data with the aid of ArcGIS, Excel and some other software.[Result] According to the second provincial soil survey, the soils of the province was averaged 7.6 in soil pH, and no soils were sorted into Grade I, Grade II or Grade III. The soils of Grade IV, Grade V, Grade VI and Grade VII were 94.49×10⁴hm², 259.0×10⁴hm², 498.8×10⁴hm² and 1.03 ×10⁴hm² in area or 11.07%, 30.36%, 58.45% and 0.12%, respectively, of the total cultivated land area. The soils of Grade IV were distributed mainly in 7 cities (Weihai, Yantai, Qingdao, Rizhao, Linyi, Weifang and Tai'an). According to the Provincial Arable Land Fertility Evaluation, the soils were averaged to be 7.2 in pH, and no soils were sorted into Grade I. The soils of Grade II, Grade III, Grade IV, Grade V, Grade VI and Grade VII were 7.48×10⁴hm², 46.09×10⁴hm²,155.4×10⁴hm², 202.8×10⁴hm², 347.3×10⁴hm² and 1.647 ×10⁴hm², respectively, or 0.98%, 6.06%, 20.43%, 26.66%, 45.65% and 0.22% of the total cultivated land area of the province. Soils of Grade III were found in 6 cities (Weihai, Yantai, Qingdao, Rizhao, Linyi and Zaozhuang) in the Jiaodong Peninsula and along the southeast coast, and soils of Grade IV in the 12 cities, except for Dezhou, Liaocheng, Binzhou, Heze and Dongying in the alluvial plain of the Yellow River. According to the Second Provincial Soil Survey, the main types of soils in the province were sorted, in terms of soil pH, as follows:Fluvo aquic soil > Paddy soil (Fluvo aquic type) > Cinnamon soil > Sandy black soil > Skeletal bone soil > Brown soil > Fluvo aquic soil, varying in the range from 8.0 the highest to 6.8 the lowest, and showing a difference of 1.2 units between the highest and the lowest. According to the PALFE, the soils exhibited a similar order, in terms of soil pH, i.e. Fluvo aquic soil > Cinnamon soil > Sandy black soil > Paddy soil (Fluvo aquic type) > Skeletal soil > Brown soil, ranging from 7.8 the highest to 6.0 the lowest, and showing a difference of 1.8 units. Comparison of the two datasets shows that the soils of Shandong as a whole dropped from 7.6 to 7.2 in soil pH in the past 30 years, and the area of alkaline arable land increased slightly, while that of the weakly alkaline and neutral arable lands decreased relatively, but the area of acidic arable land remained increasing significantly, and some of them even were acidified.[Conclusion] Since the Second Soil Survey of Shandong Province, the average soil pH of the cultivated lands had decreased by 0.4 units. The drop of soil pH was mostly found in regions of lands of Grade IV. Changes in soil pH of cultivated lands varied sharply from region to region and from type to type of the soil. Soil acidification occurred mainly in Weihai, Yantai, Rizhao, Qingdao, Linyi and Zaozhuang, especially, in skeletal soil and brown loam derived mainly acidic parent material. The Fluvo aquic soil and Cinnamon soil derived from Yellow River alluvial deposit and limestone were both alkaline, relatively high in pH. Natural acidification, crop harvest and improper use of chemical fertilizers are the main factors triggering decline of soil pH and even acidification in Shandong.