Abstract: As the largest basin area in Chuxiong Prefecture of Yunnan Province, Yao'an basin area is a core area for plateau-based modern agriculture. However, long-term intensive cultivation and improper fertilization have led to rapid soil fertility decline. To systematically assess the soil fertility status, the researchers collected 456 surface soil samples to analyze 11 fertility indicators, including soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), total potassium (TK), boron (B), molybdenum (Mo), copper (Cu), zine (Zn), manganese (Mn), total iron (TFe), and pH. The modified Nemero index method was employed for comprehensive fertility evaluation. The results showed that soil pH value in the study area ranged from 5.01 to 9.19, with an overall weakly alkaline condition, but localized acidification occurred (accounting for 10.86%). SOM and TN contents were abundant and showed a highly significant positive correlation (r=0.914), and their spatial distributions were highly consistent, jointly influenced by parent material and agricultural activities. The comprehensive fertility evaluation indicated that the overall soil fertility in the area was classified as Grade Ⅱ (moderate), accounting for 98.96% of the area, with no Grade Ⅰ (fertile) soil, and Grade Ⅲ (infertile) soil was scattered sporadically in the southeastern, south and northern parts of the basin area. This method effectively highlights the limiting role of fertility constraints, and the evaluation results could objectively reflect the current soil fertility status of the basin, that is high organic matter and nitrogen content, relatively insufficient trace elements, and moderate overall fertility. These findings could provide scientific basis for cultivated land protection and rational fertilization in Yao'an County.