A new methodology for the division of water environmental functiona1 zones in Jianhu Lake, Zhajiang Province, is proposed.The division process is further designed.By means of the aerial photograph interpretation, the lake-river system's cause of formation investagation, and sko-economic and environmental data collection, the techniques composed of overlay-mapping, water quality dus ter analysis and O.intergrated evaluation are used.Based on the area units of naturalregion, four functional zones have been setup for Jianhu Lake water environment.The study results show that the suggested methodology is an effective way to solve functional zones division, because it not only has the semi—quantitative advantage but also can provide scien-tific basis for making rational use of water resources and protecting water quality.The divisional results of four functional zones have been applied successfully to Jianhu Lake environmental capac-ity and water quality planning, to the daily management by local environmental admnistrative depayments.