Dianchi Lake is one of the most serious of eutrophication of lakes in Western China. Phosphorus is considered as the limiting factor causing for eutrophication and harmful algal blooms in Dianchi Lake. In this study, Dongda River basin, one of the rivers entering into Dianchi Lake, was chosen and the phosphorus forms and spatial distribution were investigated. The results showed that: 1) the phosphorus was significantly accumulated in downstream. 2) Land use type had significant impact on phosphorus accumulation, and facility agriculture was the most important factor in the accumulation of soil phosphorus. 3) The phosphorus was most heavy in northeast of the study area near the Dianchi.