Abstract: Carbonate rock buried hill is one of the important oil-gas reservoirs in Bohai Sea. Taking Z Oilfield, the key development target in Bohai Sea area as an example, the characteristics, formation mechanism and geological development model of carbonate rock reservoir are comprehensively analyzed by using basic data such as drilling and logging, cores, microscopic thin sections and seismic data. The results show that the lithology of carbonate rock buried hill reservoir is mainly dolomite, with the reservoir spaces of intergranular pore, fracture and dissolution pore. Carbonate rock buried hill reservoir is mainly controlled by sedimentary, diagenetic and structural factors. Combined with the characteristics of single well and vertical karst zonation, the buried hill can be divided into surface weathering zone, vertical seepage zone and bedding dissolution zone. Under the influence of multiple factors such as diagenesis and structure, the reservoir in the upper oil formation is more developed than that in the lower, with full-region development for the former and limited development for the latter. The karst zoning and geological model of reservoir distribution provide the basis for next adjustment and potential tapping direction.