The research on the incised valley of carbonate platform is mostly based on the field outcrop of Upper Cretaceous in Oman. Based on the drilling cores, logging and 3D seismic data of the Upper Cretaceous Mishrif Formation in H Oilfield of Iraq in the Middle East, combined with regional sequence stratigraphy, this paper studies the important sedimentary microfacies types of incised valley developed on carbonate platform from the aspects of sedimentary cycle, lithofacies, logging response, plane distribution and vertical evolution of seismic facies, and discusses its significance. The research shows that: (1) There is a incised valley in carbonate platform in MB2-1 submember of H Oilfield. The interior of the incised valley is mainly filled with micrite limestone (obviously different from the underlying grainstone), and the particles become thinner then coarser upward. The logging curve of the incised valley has the characteristics of box shape. For the incised valley, the seismic section shows strong amplitude reflection with parallel-near parallel and short axis, and it is similar to the river shape in the plane while more straight with clear boundary. (2) It is eroded into a valley in the late high-stand domain of SQ3 (the late sedimentary stage of MB2-1 submember), and rapidly filled with micrite limestone in the transgressive stage of SQ4. The bottom of the incised valley represents regional sequence boundary. (3) The MB2-1 incised valley is compact as a whole, which can be a transverse barrier of the reservoir. The discovery of incised valley in carbonate platform is of great significance for the identification of sequence boundary and the study of reservoir heterogeneity.