Effects of pen fish culture in Taihu lake were studied and summarized. During 1984 to 2001,pen fish culture of Taihu lake developed from extensive models to intensive and high-returned ones, the cultured species were shifted from fishes to crabs. Pen fish culture has caused eutrophication and detrimental effect to the ecological environment and fishery. The measures of sustainable development for pen fish culture and ecological environment protection were suggested.