Fertilizer nitrogen mainly remains in the form of nitrate nitrogen. If not taken up by crops, it will be leached downward to subsoil by rainfall and irrigation water, negatively impacting soil and water system. Ningxia Irrigation District is the representative irrigation farming region in the upper stream area of the Yellow River. The paddy-upland rotation is still the typical agricultural model in this irrigation district. the crude farming methods are used in the paddy planting, such as uncontrolled irrigation and excessive fertilization, therefore there is a high accumulation of the residual nitrate nitrogen in soil after the harvest. During the long fallow period in the irrigation district; the residual nitrate nitrogen tends toward leaching due to freeze-thaw and wind erosion under the condition of winter irrigation in order to keep the soil moistures. The resin core technique has been applied to study the nitrogen mineralization in recent years. This method can absorb the leaching nitrate nitrogen directly and do not need to estimate the leakage; moreover causes slight disturbance to the soil, and therefore has been considered as an ideal method to study the nitrate nitrogen leaching losses in field. A filed experiment was conducted in paddy of Ningxia Yellow River irrigation district with three treatments including normal fertilization (CK), 4500kg/hm²(T₁)and 9000 kg/hm²(T₂)pig manure, respectively, on the basis of the normal fertilization. The undisturbed soil columns were obtained by driving the different length stainless steel tube into the soil vertically after the harvest. The stainless steel tubes are 42, 52, 102 centimeter long and the length of the wedge surface is 10 centimeter. The three different length stainless steel tubes are one unit; three units were set up for each experimental plot. The cut-and-dried aluminum plastic plate, resin bag, aluminum plastic plate, antiskid axis were sequentially enclosed in after removing the 2 centimeter soil at the bottom. The stainless steel tubes were cultivated on the original place. The soil samples, collected around the stainless steel tubes, were classified into 3 groups according to depth (0-30, 30-60 and 60-90 cm).The soil nitrate-nitrogen, ammonium nitrogen, organic matter and active organic matter content were measured at the start and end of the assay. The nitrate nitrogen leaching losses of soil at the depth of 30, 60, 90 cm were measured by the method of resin core in the fallow period. For the normal fertilization, the largest nitrate nitrogen leaching loss was found at the depth of 90 centimeter, which is 1.10 and 1.13 fold higher than T₁ and T₂, respectively. However, the largest nitrate-nitrogen leaching losses in T₁ and T₂ appeared at the depth of 60 centimeter, which are 4.47kg/hm² and 4.21kg/hm² respectively, and 1.50 and 1.42 fold increases compared to CK, respectively. Application of organic manure can reduce the nitrate nitrogen to leach downward to subsoil on the basis of the normal fertilization. The increase nitrate nitrogen leaching losses at the depth of 60cm seems to facilitate the further leaching, however, in the mode of the paddy-upland rotation, because the irrigation amount is normally reduced during the upland period and also the nitrate nitrogen is absorbed by crops, the leaching losses will thus be significantly decreased.