Soil pH is an important attribute of soil produced by the combination of biological，climatic，geological and hydrological factors during its formation，and it is an important indicator of soil chemistry and fertility.Though the spatial interpolation analysis of a large number of soil sample data from Jilin province in the two time periods of 2008(2005—2008)and 2018(2015—2018)，the spatial and temporal variability characteristics of soil pH in the cultivated layer of Jilin farmland were clarified，and compared with the data from the 2nd national soil survey data(1978)to analyze the trend of soil pH changes.From 1980 to present，the average soil pH changed from 0.03 units per year in pH1978-pH2008 to 0.02 units per year in pH2008-pH2018.Although the average soil pH still decreased to some extent during the period from 2008 to 2018，the acidification trend slowed down to a certain extent compared with the previous 30 years(1978—2008).The pH of different soil types decreased differently，the pH of meadow and rice soil decreased significantly by 1.3 and 1.6，respectively；the pH of black soil decreased by 0.4；While the change of pH in albic bleached soil and dark brown soil was relatively small.However，the pH of saline soil increased by 1.5，the average pH changed from 0.01 per year in pH1978-pH2008 to 0.12 in pH2008-pH2018，which showed that salinization of saline fields increased.Spatially，the soil pH in Jilin farmland decreased from west to east.Acidic soils accounted for 5.7% of the total arable land area, weakly acidic soils accounted for 36.9%，neutral soils accounted for 32.4%，weakly alkaline accounted for 24.3%, alkaline soils accounted for 0.7%.Compared with in 2008，acidic soil decreased by 1.6%, weakly acidic soil increased by 2.9%，neutral soil increased by 2.5%，and weakly alkaline soil decreased by 4.2%, alkaline soil increased by 0.4%.We should control the excessive application of chemical fertilizers and reasonably add organic materials such as straw and organic fertilizers to alleviate the trend of soil acidification and alkalization，and achieve the improvement of soil fertility and stable supply of nutrient in Jilin province.