Abstract: In recent years, the agricultural nonpoint pollution has threatened the water quality protection of headwater area in reservoir. To prevent the environmental pollution, protect the water quality of the ground water body,and to exert enough the productive potentialities of resources, it is important to control nonpoint pollution in the protection zone of headwater area of a reservoir at present. Pretank technology is one of the effective ways to prevent the nonpoint pollution in headwater area of reservoirs because it has such advantages as low expenses, suitable for many kinds of conditions. According to the special geographical characters and some characters of the nonpoint pollution in headwater area of reservoirs, this paper explains the composition of pretank and its water quality purification mechanism, proposes the capacity of a reservoir and site selection for pretank,and analyses detailedly pretank ecosystem and aquatic biological construction. Furthermore, this paper put forward the limitation of pretank in the course of usge. Owing to pretank technology which can reduce pollution load organically outside reservoir, especially the nitrogen, phosphorus in the stream that flows into reservoirs, this technology has extensive potential application prospects.

Key words: pretank, nonpoint pollution, pollution control, zoology formation, headwaters area of reservoir