Reef-building was controlled by the community succession, sea-level elevation and basement changes caused by tectonics. Six kinds of reef-building communities have been sorted out, which possessed different compositions and occupied respective ecological sets. Types and thrivingness of communities were distinctive and replaced one after another in the four stages of reef development. Sedimentary cyclothems are clearly discernible in the reef-facies strata, which could divide into five sequences and fourteen types of parasequences. These se-quences represent varied degrees of rising-falling cycles of the sea-level, which limited community distributions and reef-building velocities. Based on the analysis of community succession, sea-level elevation and paleo-geographic variation in the working area, four stages of tectonic evolution in the Hercynian can be distin-guished , which made up two open-closing cycles between the Qaidam plate and the Qiangtang plate. The reefs were built in the open-closing transitional period of the mid-late Hercynian, while southern margin of the Qaidam plate kept a stable condition continuously.