Public welfare forest can play a significant ecological benefit by improving the understory vegetation and soil conditions.However,the composition of understory plants and soil characteristics of the public welfare forests in central Yunnan are not clear.In this study,the species composition and soil physicochemical properties of four typical public welfare forests (Alnus Nepalensi,Pinus Yunnanensis,Castanopsis Orthacantha and Pinus Armandii)in Yuxi were investigated.The species diversity and soil properties of understory shrubs and herbaceous plants were analyzed,and the relationship between species diversity and soil properties was revealed.The results showed that:1)The species composition under Pinus yunnanensis forest was the most abundant (both shrubs and herbs had the highest number of species,both diversity index and richness index were the highest).The lowest species diversity in shrub layer and herb layer were Pinus armandii and Castanopsis orthacantha;2) the soil organic matter of four kinds of public welfare forest were rich,the contents of soil total nutrients (total nitrogen,total phosphorus,total potassium)and available phosphorus in Alnus nepalensis were significantly higher than those in other forests,the soil bulk density,total nitrogen,total potassium and available potassium contents of Castanopsis orthacantha were the lowest;3)Soil available phosphorus,total phosphorus,total potassium and bulk density were the key factors affecting shrub species diversity under public welfare forests,the key factors affecting herbaceous species diversity were soil total phosphorus and pH.Species diversity under public welfare forests in central Yunnan was closely related to soil properties.Attention should be paid to soil acidity-alkalinity,compactness and selective regulation of nitrogen,phosphorus and potassium,so as to improve the structure of understory shrubs and herbaceous plants to achieve the best benefits.