| With the rapid development of the economy and society, agricultural non-point pollution problem becomes more and more serious. The characteristics of Non-point source pollution are harmfulness with a wide distribution range, the great randomness and the ambiguity in the mechanism of the formation process. It is very important as the polluted source reduces the water quality. Therefore, agricultural non-point pollution research and management have important meaning for improving the rural ecological environment and ensure the safety of the water environment. In this study LingWu irrigation area of Ningxia is Research object,the method used was a combination of macro analysis and microcosmic experiment, field test and indoor analysis, experimental study and numerical analysis. Firstly, on the base of the analysis of agricultural irrigated area non-point pollution, calculated the polluted loads in the different irrigated areas and evaluated the irrigation return water quality, thus, suggest preventive treatments about agricultural non-point pollution and offer the technical criterion for promoting the water environment in irrigation. To sum up, the conclusion of the paper is as follows:(1)Base on the survey and collecting data in Lingwu irrigation area Ningxia province, the method of the same standard pollution emission coefficient and the remote sensing technology were used to analyze the Non-point source polluted load of total nitrogen TN,total phosphorous TP,chemical oxygen demand COD,NH3-N from the sources of the farmland runoff, the livestock breeding, the domestic sewage in the villages and so on. The results showed that the total quantity of pollution emission into the water was 1.68×106Kg/a kg/a in the Lingwu irrigation area, in which the COD was 1.42×106 Kg/a, the TN was 1.57×105Kg/a, the NH3-N was 7.40×104Kg/a,the TP was 3.79×104 Kg/a accounted for the total pollution emission 84.10%,9.28%,4.38%,2.25%. From the date, we find that COD is the greatest polluted source, the second is TN, the third is NH3-N and the last is TP.(2)By using the method of Grey Clustering to evaluate the water quality at the West-big channel in the Lingwu irrigation area, Ningxia province, the results showed that the water quality was belong to five levels of the water standard, in the long term in the monitoring section, because lots of wastewater without any treatments discharged into the West-big channel from April to September; the water quality of month of the West-big channel was belong to five levels of the water standard, due to too much basic fertilizer used at the period of rice soaking, which lead to the high level of TN concentration in the water-back between April and May; owing to the decline of irrigation water and fertilizer, simultaneously, the dilution of rain, the water quality improved a little, which was under four levels of the water standard during the period of June and August, and moreover, as a result of the sharply decline of irrigation water, the water quality was belong to five levels of the water standard as a result of the a mass of pollutant from the upper farms.(3)In conclusion, the water quality was influenced by decomposing waste water, irrigated water, and excessive fertilizers in agriculture and so on at West-big channel in Lingwu irrigation area. For the pollution of breeding waste water, we should start from source control, promote cleaner conduction and ecological breeding and achieve waste reduction, harmless and ecological. To reduce pollution excessive use of fertilizers for agriculture should be avoided, promoting the best farm nutrient management, reducing the use of fertilizers and adjusting and optimizing rural industry structure by introducing actively high-tech achievements,developing green agriculture and ecological agriculture control the type and quantity of non-point source into water body, improve the irrigation return water quality, relieve irrigation return water of the Yellow River water pollution and thus to protect the water environment.
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