The study of the diagenesis and reservoir formation mechanism of carbonate rocks from the Cambrain in Eastern Tarim Basin was based on some data from core analysis, thin-section identification and cathodoluminescence experiments. The result shows that there were obvious diagenetic effects after sedimentation, some had constructive effects to the reservoir, such as dolomitization, dissolution and disruption. Some,as for compaction,pressolution,recrystallization and sillication were destructive to the reservoir in the study area. It also shows that the main reservoir spaces were intergranular pores, intergranular dissolution pores, dissolved pores and fractures which were not filled. The main reservoir types were dolomite dissolution pores and dolomite dissolution fracture pores. Dolomitization provided the basic condition to the reservoir, the late hydrothermal solution was crucial to the reservoir and the disruption later improved the permeability of the reservoir. Dolomite was more enriched in the area which slope and platform superposed with fractures. In this area hydrothermal solution and structural fracture were more developed thus make it the favorable zone of study area.