Abstract: On the basis of the occurrences of stratified carbonate—algal stromatolites and their associations with primary red algae, in combination with the data on lithostratigraphic sections in the Yuxi and Eshan districts as well as the representative literatures on the carbonate rocks in the Middle Proterozoic Dalongkou Formation of the Kunyang Group in central Yunnan, the diagenetic environments of the carbonate sediments in the Dalongkou Formation may be divided into the subtidal low-energy zone in the platform facies region, the subtidal high-energy zone in the platform margin facies region and the subtidal low-energy zone in the inner shelf facies region.