Soil quality is a critical indicator of ecosystem health and sustainable land management. The Dianchi Lake watershed, as a key ecological area in the southern plateau of China, has recently faced threats to soil quality due to changes in land use practices. This study aims to assess the soil quality of five typical land use types in the watershed and investigate the effects of different vegetation types on soil physicochemical properties. The minimal dataset method (MDS) and principal component analysis (PCA) were employed to process the data and identify key soil quality indicators.The results indicate that: (1) A comparative analysis of the physicochemical properties of soils in five typical forest types in the Dianchi Lake watershed revealed that the soil quality of mixed forests, pure forests of Chinese pine, and pure forests of Eucalyptus deglupta significantly surpassed that of artificial eucalyptus forests. The mixed forest exhibited higher organic matter and total nitrogen content, while the Eucalyptus deglupta forest demonstrated strong water retention capacity. The pure Chinese pine forest performed well in nutrient supply and fertility maintenance. The soil quality of shrub forests was intermediate, with zmoderate levels of organic matter and total nitrogen. (2) The MDS was used to evaluate the soil quality index (SQI) across three soil layers for different forest types. Results showed that the SQI was highest in the pure Chinese pine forest at the 0-20 cm layer, in the Eucalyptus deglupta forest at the 20-40 cm layer, and in both the Eucalyptus deglupta and mixed forests at the 40-60 cm layer. The average SQI values were as follows: Eucalyptus deglupta (0.60) > Chinese pine (0.54) > mixed forest (0.47) > shrub forest (0.33) > artificial eucalyptus (0.20). (3) The MDS analysis demonstrated a strong correlation with the total dataset (TDS), with a fitting performance of R2 = 0.69, confirming the effectiveness of MDS in soil quality assessment.The findings provide a scientific basis for soil management in the Dianchi Lake watershed, recommending the promotion of Eucalyptus deglupta mixed planting in water conservation areas and regions severely affected by soil degradation to maintain soil organic matter and improve water retention capacity. Additionally, it is suggested to implement mixed planting and rational irrigation measures for artificial eucalyptus forests to restore soil quality, while enhancing the coverage and soil conservation capacity of shrub forests to sustain soil fertility and ecological functions.