Abstract: The saturated irrigation tests were carried out in a couple of lysimeters (the levels of groundwater are all 1m) built in the field of Huaibei Plain.The irrigating water was taken from Kuiriver of Xuzhou.The results obtained are summarized as follows:Although ammonium-N is as high as 5.35mg/L in the wastewater,it con't pollute the groundwater directly when wastewater irrigates it in the soil in a normal condition,because ammonium-N is sorbed mainly by soil colloids and is difficult to move.When wastewater moves down,it leaches washing nitrite and nitrate that have accumulated in the soil,and makes their concentrations increase rapidly.After irrigating,with the variation of moisture,oxygen and pH value,the ammonification,nitrification and denitrification are successively the majorcauses of nitrogen trasformation in the soil.During ten days of irrigation,NO₂^- and NO₃^- arisen from leaching and nitrification bring about serious pollution in the shallow groundwater.