Jiangshuigou reef is one of well developed Upper Permian reefs in the Huaying Mountains.The reef-building organisms are calcareous sponges

hydrozoans

tabulozoans and Archeolithoporella etc.The development of the reef can be divided into two main cycles and each of them contains three stages

that is

stabilization

colonization and diversion.Eight communities and seven guilds have been established according to fossil assemblage.The abundant vadose silts and dissolved caves filled with oolites and pellets indicate that the reef had been exposed several times during its development.The eustasy was the ex-ternal factor that controlled the development of the reef

while the ecological evolution of the organisms was the internal factor.The extinction of the reef-building organisms was related to the mass extinction of organisms between Permo-Triassic boundary.So the reefs in the Huaying Mountains are the highest ones in the Paleozoic.