Abstract: Four genetic types of diagenesis are defined for the dolostones as:syngenetic,para-syngenetic di-agenetic and epigenetic dolostones, which are mainly attributed to the Ordovician systems partly to the upper and lower Cambrian systems. Syngenetic dolostones formed in an environment of under water evaporation can be cover rocks while those in a diagenetic environment of overwater evaporation, and diagenetic dolostonss in a snallow buried diagenetic environment are of fairly good reservoir rocks. But the secondary lenticular dolostones occurred beneath the unconfority of the Huaiyuan Period are poor reservoir rocks.