In order to clarify the evolution characteristics and main controlling factors of cultivated soil fertility in different regions of Hunan Province，based on the second soil census in 1980 and the monitoring data of cultivated land quality in 2017(including pH，organic matter，total nitrogen，available phosphorus and available potassium). The Fuzzy method was used to calculate the soil comprehensive fertility index，and the Random Forest Model was used to analyze the main controlling factors of soil fertility. The results showed that the pH of cultivated soil in Hunan Province showed a downward trend from 1980 to 2017. The average pH values in the northern Hunan(plain area)，the central and eastern Hunan(hilly area)，the southern Hunan (hilly area)and western Hunan (mountainous area) were decreased by 0.29，0.41，0.19 and 0.48，respectively. The content of soil organic matter in the northern Hunan，the southern Hunan and the western Hunan remained basically stable，with an average range of -3.1%-4.4%. The content of soil organic matter in the central and eastern Hunan increased significantly，with a range of 18.9%. The total nitrogen，available phosphorus and available potassium of cultivated land in all regions showed an upward trend. The maximum increase of soil total nitrogen and soil available potassium in central and eastern Hunan was 36.1% and 42.6%，respectively，and the maximum increase of soil available phosphorus in southern Hunan was 229.8%. From 2018 to 2017，the comprehensive index of cultivated land soil fertility in Hunan Province was concentrated in the range of 0.6-0.8，and the fertility level of the whole province was improved. The random forest model analysis pointed out that after nearly 40 years，the main controlling factors of cultivated land soil in different regions were different. The main controlling factor of cultivated land soil fertility index in the northern Hunan was the available phosphorus. The main controlling factor of soil fertility in the eastern and southern Hunan was available potassium，and total nitrogen in the western Hunan.