Aiming at the early waterflood breakthrough which caused by the "abnormal high permeability zone" in the development of the Kh2 reservoir of Khasib Formation of AHDEB oilfield in Iraq, we carried out the research on the Khasib reservoir evolution and genesis of the abnormal high permeability zone by using drill core, imaging logging and geochemistry data. The results indicate that the karst reservoir of Kh2 forming is controlled by the depositional karst and multiple phase deep buried karst. The reservoir evolution can be divided into three stages: Syndiagenetic stage, shallow-medium buried of organic acid dissolution and alteration stage, and rapid settlement of deep burial period of hydrocarbon filling stage. The depositional karst featured as the fabric selective dissolution of vertical infiltration, which forming the two high porosity zones which are the Kh2-1-2 of the intraclast intergranular pore bearing zone by the primary high connectivity pore of the intraclast grainstone, and the Kh2-3-2 of the algal moldic pore bearing zone by well solubility of algal debris. During the diagenesis period, the reservoir is under through the buried karst that is inherited karstification in non-fabric selective dissolution way based on the post-depositional pore of the reservoir, and featured as the strike-slip fault(connected the source rock and reservoir)as the fluid migration path, the acidizing fluid by from organic substance degradation as the dissolution media, the post-depositional high porosity zone as the dissolution carrier(the Kh2-1-2 and Kh2-3-2 zone). Owe to the different pore character of vertical zones in reservoir have the different karstification characteristic, and the openness of strike-slip faults controlled by the tectonic activity, after the depositional karst and at least two stages deep buried karst, finally formed the two "abnormal high permeability zones" that are intraclast grainstone zone of Kh2-1-2 show as the weak compaction and cementation, main pore type is intergranular and intergranular dissolved pore with excellent connectivity, pinhole vug, and moderate-poro high-perm property, and the algal debris packstone zone of Kh2-3-2 show as the weak cementation, high plane porosity, coexistence of different pore types including the moderate-micro vug, dissolution fracture, and micro matrix micro-pore with high heterogeneity and high-poro moderate-perm property. The intraclast grainstone zone is fluid flow passage to cause the early water breakthough in water-flooding. In summary, high connectivity origin intraclast intergranular pore, the pore integrity was conserved during the depositional karst period, long-term shallow buried diagenetic environment(90~20 Ma), favorable potential area for fluid migration(the top end of the fault), good coupling relationship of the hydrocarbon fluid filling and fast formation burying period, all of these, which make the Kh2-1-2 zone to forming the abnormal permeability zone.