Abstract: In order to reveal the mechanisms and causes of agricultural non-point source pollution, the Zhanghe Irrigation District in Hubei Province was selected to conduct the study on the basis of analyses of field experiments in this paper. The influencing factors and patterns of phosphorus losses in the agricultural drainage water of paddy rice and corn fields were studied. The results showed that rainfall intensity, crop type and agricultural tillage management (including irrigation techniques and fertilizer application, etc) are the crucial factors influencing the loss of phosphorus from agricultural drainage. Besides, soil physical and chemical properties, topography and land slope also affect the losses of phosphorus from farmland to a certain extent.