Abstract: With the effective control of source pollution, nonpoint source pollution becomes more outstanding. Indeterminacy of time, way and quantity brought much difficulty to the management of agricultural environment and crippled availability of control measures. The carriedout research was most focused on calculating pollutant load and selecting controlling measures. But the influence factors were devoid of thorough understanding. According to the process of engendering pollution and pollution characteristic, all kinds of factors affecting nonpoint source pollution are analyzed in this paper. These factors include the pollutant gross at present and its changing direction, environmental purification competency, farm activity, climate and hydrological condition, and especially socioeconomy function. Dominants influence factors changing space with and time and the discrepancy among different terrains are pointed out. And the necessity of basic pollution investigation and database is emphasized, which will contribute to further study in the ThreeGorge Area.

Key words: nonpoint source, pollution characteristic, influence factor, terrain discrepancy