The Upper Cretaceous Mishirif Formation is the main oil producing reservoir in Eastern Rub Al Khali Basin. At present, the research on the difference of reservoir pore properties between the Mishrif Member 1 (Mishrif-1) and Member 3 (Mishrif-3) is relatively weak. On the basis of the analysis of core, thin section, gas injection, mercury injection and nuclear magnetic resonance (NMR), the reservoir space types and pore structure types of Mishrif Formation are systemically studied. The results show that: (1) The rock types of Mishrif Formation include micritic bioclastic limestone, bioclastic micritic limestone, and rudist limestone. There are mainly intragranular solution pore, intergranular pore, mold pore, biological cavity pore, and intergranular solution pore in the reservoir, indicating that it is a porous reservoir. (2) The reservoir of Mishrif Formation has obvious facies-controlled characteristics. The high quality reservoirs are concentrated in microfacies including reed and bioclastic shoal of Mishrif-1, bioclastic shoal and rudist reef-shoal of Mishrif-3, with an average porosity of more than 20， and an average permeability of more than 100×10-3 μm2 , which is a high porosity and high permeability reservoir. (3) The mercury injection curve of the reef in Mishrif-1 is oblique, the NMR curve is serrated, the pores are large biological cavities with pore size of 50-100 μm, and the irreducible water saturation is low. The mercury injection curve of Rudist reef-shoal in Mishrif-3 is oblique, and the NMR curve is bimodal-serrated composite, mold pores and biological cavities are developed with pore size of 1-100 μm, and certain intergranular dissolved pores are developed with poresize of 0.4-1 μm at the same time, and the irreducible water saturation is low. The mercury injection curve of bioclastic shoal in Mishrif-1 is oblique, the NMR curve is bimodal-serrated composite, mold pores and intergranular dissolved pores are developed with pore size of 0.1-10 μm, and the irreducible water saturation is low. The mercury injection curve of bioclastic shoal in Mishrif-3 is oblique, the NMR curve is serrated, the pore size distribution is not concentrated, and the pore types are diverse, mainly intergranular dissolved pores.