Karst reservoir takes an important role in the carbonate reservoir, whose primary formation mechanism, however, has been considering as the karstification controlled by phreatic water table. In this paper, based on the knowledge of geological setting of Ym2 area in Tabei uplift, in combination with the integrated analysis of lithology, geochemistry and the controlling factors of karstification, it has been believed that fracture-cavern reservoir could be formed in carbonate strata by the karstification in the area with the continued depositional sequence. Based on the observation of cores and thinsections, the analysis of geochemistries, such as carbon and oxygen stable isotope, strontium isotope composition, rare earth element, electroprobe, cathodolumine- scene, and fluid inclusion, etc, has been maken on the different types of calcites, and furthermore, the properties and provenance of the diagenetic fluids has been analyzed, and it has been concluded that the meteoric water is the main karst fluid, which exerted the primary effects on the formation of porosities, whereas hydrothermal fluid just modified the reservoir lately. Based on the analysis of the relationship between the tectonic evolution and formation of structure and development of strike-slip faults, it could be known that the uplift of structure and development of strike-slip faults is prerequisite to the karsitification. Furthermore, a new structure and fault-controlled meteoric karstification is proposed, which occurred by meteoric water descending continuously into the fracture systems within the carbonate strata along the faults through the overlaid siliciclastic beds. This new karstification promoted the knowledge of formation machenism of carbonate reservoir.