Abstract: Based on previous studies and existing exploration data, the study on microfacies types and characteristics of carbonate rocks of Ma5_1~Ma5_2 in Ordovician Majiagou formation was carried out, which is located in the southeast of Shanbei slope in Ordos basin. Through the core observation, casting thin slice analysis and other experimental methods, combined with rock types, sedimentary texture, structure, paleontology and other information, open platform facies which were developed in Majiagou formation were identified. Main microfacies types as follows: the tidal flat set mud microfacies, tidal flat microfacies clastic beach, tidal flat microfacies, karst tidal flat storm microfacies, cream set microfacies, plaster tidal-flat sedimentary microfacies, tidal flat, ash, mud, cloud mixed sedimentary microfacies. The distribution of the microfacies and evolution characteristics were analyzed.