Phosphorus as a major nutrient element in water ecosystems is a key factor affecting algae growth in rivers. This paper adopts the sequential extraction method for phosphorus fractionation to study the distribution of phosphorus forms in riparian soils and peripheral river sediments, then to analyze the relationship between different phosphorus forms and their significance within a watershed environment. The results show that: 1) the contents of NH₄Cl-P, BD-P, and HCl-P in riparian soils are more widespread than those in river sediments, 2) the distribution patterns of phosphorus fractions in different catchments of Jianxi Basin are varied for soil and sediment, and 3) the ratio of BAP/TP is the highest in Chongyangxi catchment and the lowest in Songxi catchment. Phosphorus in riparian soils is mainly affected by agricultural activities, significantly for NaOH-P and HCl-P. And phosphorus forms in sediments are obviously affected by domestic sewage. The phosphorus contents and fractions in riparian soils change more significantly than those in river sediments.