Abstract: Reservoir heterogeneity includes microheterogeneity and macroheterogeneity. The central area of Beibao is located in the west of Nanbao depression, Dongying Formation is one of the major reservoirs in Beibao area. Its reservoir heterogeneity was studied by analysis of core thin sections, cast thin sections, characteristics of cores in scanning transmission electron microscope, X-ray test data and data of well log reservoir evaluation. The study shows that reservoir of Dongying Formation is lithologically characteristerized by complex rock composition, high contents of unstable components, poor sorting and shale sand structure. The compaction, corrasion and conversion of clay minerals in the Dongying Formation are very common, but the diagenetic features change greatly. Besides, the reservoir has middle-low thin throat structure and its connectivity is very bad, consequently reservoir has higher microheterogeneity. Reservoir macroheterogeneity is also high. Its internal longitudinal permeability has obvious differences and the value of permeability heterogeneity parameters is greater. Inter-layer heterogeneity of reservoir is similar to internal heterogeneity. Reservoir plane heterogeneity is higher due to bad connectivity, low effective sand coefficient and changes of heterogeneity parameters on the plane. By using fracturing methods, reducing reservoir heterogeneity and improving reservoir connectivity, the efficiency of development can be increased.