Abstract: In order to find out the degree and spatial distribution of soil acidification in southwestern mountainous region of Hubei Province. The author took Xuan’en County of Enshi City as a typical region to analyze the change tendency of soil pH value by comparison of pH data that came from the second national soil survey and the project of soil testing and fertilizer recommendations. The result showed that: the average arable soil pH value of Xuan’en County was reduced by 0.97 units, and the areas of strong acid soil (pH<5.0) were increased by 53.0% in past 30 years. The spatial distribution of soil pH in Xuan’en County had less change, but the pH of arable soil all declined in varying degree, the falling range of soil pH was the most in Chunmuying Village, and the least in Xiaoguan Village. The pH all decreased to various degrees among the soil types in Xuan’en County. Brown soil, psephite mountain yellow brown soil and quartzose mountain yellow brown soil had a large decrement of pH value, and limestone mountain yellow brown soil had a small decrement of pH value. The annual pH decreasing rate of tobacco plantation soil in recent 10 years was 2.75 times than the previous 20 years. Soil pH value was extremely significant negative with the total P and available P, and it might be one of the main factors of soil acidification to use a large number of acid phosphate fertilization in this area.