According to the characteristics of lithofacies, seismic section facies and logging facies, combined with the data of thin sections of rocks, the types and characteristics of sedimentary systems developed in the lower Cretaceous Nantun Formation in Beixi area, Beier depression, Hailaer basin are systematically studied. It is considered that the Nantun Formation in the study area mainly develops fan deltaic sedimentary systems, and three types of subfacies: fan delta plain, fan delta front and front delta are identified. There are eleven microfacies, i.e. subfacies, plain distributary channel, plain distributary channel and front underwater main channel. On this basis, the fan delta sedimentary model of Nantun Formation in Beixi area of Beier depression is established, which has certain reference value for the prediction of dominant reservoirs.