Abstract: Yuqiao Reservoir Watershed is divided into four pollution-controlling regions of phosphorous loss by using clustering method, taking 28 sub-watersheds as regionalization objects. Six impacting factors of agricultural non-point source phosphorous pollution were regarded as regionalization factors, including 4 factors of Universal Soil Loss Equation (USLE): rainfall-runoff factor (R), soil erodibility factor (K), landform factor (LS), vegetation factor (C) as well as soil available phosphorus (SAP) and fertilizer phosphorus application rate (FP). It was found that the important regionalization factors greatly effecting the regionalization results of agricultural non-point phosphorous were rainfall-runoff factor (R), landform factor (LS), vegetation factor (C) and fertilizer phosphorus application rate (FP), which had great variability among four pollution-controlling regions. While soil erodibility factor (K) and soil available phosphorus (SAP) had little importance for the regionalization because of their small variability among different regions. The natural eco-environmental characteristics, phosphorous pollution characteristics and its major impacting factors in each region were analyzed, and based on that, the pertinent control measures were proposed, providing scientific foundation for carrying out the in-depth study in the following work.