Taking L reservoir in Laojunmiao Oilfield as the research object, this paper aims to solve the problem of poor adaptability of conventional reserve calculation methods in complex fault block reservoirs. By integrating logging interpretation, seismic inversion and production dynamic data, using Direct software, a three-dimensional geological model is constructed by combining deterministic modeling and stochastic simulation, and the spatial distribution of sand bodies is accurately described by using facies-controlled modeling technology. The parameter fields of porosity, permeability and oil saturation are established by combining geostatistics, and dynamic reserve correction is introduced to constrain the productivity of static reserve calculation results. The results show that the petroleum geological reserves calculated by this method are 24.244 million tons, and the fitting error with the production dynamic history is only 4.3%, which effectively solves the problem of inaccurate calculation of reserves near faults, and the prediction result of sand body connectivity in the model is 89% consistent with later drilling. The research proves that 3D geological modeling technology can significantly improve the reliability of reserves calculation in complex fault-block reservoirs.