Riparian woodlands play a significant role in hosting plant diversity and maintaining soil and water resources. However, riparian woodlands are highly sensitive to fluvial and human disturbances, and most are now degraded as a result. In this study, we analyze variation in soil nutrients and plant diversity and their relationships in riparian woodlands along the middle and lower reaches of the Yellow River in China, based on field investigation. Our results indicate that soil nutrient content and plant diversity were lowest in plots located closest to the river. Specifically, we found a hump-shaped relationship with increasing distance from river. This result can be attributed to the intermediate disturbance hypothesis,which explains that species diversity increase at intermediate disturbance levels. However, total species richness within each subzone was greatest close to the river, due primarily to the high level of species turnover observed among plots located closest to the river. Soil nutrients in the riparian woodlands were positively correlated with plant diversity across all distances. Specifically, soil TC, NO₃^--N, and A-P contents were significantly correlated with plant species richness and diversity. This relationship also conformed to a hump-shaped response curve between species richness and soil nutrients, though species richness increases with increasing nutrient levels. Results from this study can provide a basis for sustainable management of riparian ecosystems.