Based on a synthetic analysis of core description as well as thin section and logging data in combination with sedimentary marks of lithology, paleoclimate, sedimentary structure, and the depositional background of weak tectonic movement and flattened palaeotopography, the authors hold that the lower segment of the Xingouzui Formation is of a shallow water delta depositional system. The shallow water delta has the following characteristics: 1)there exist well-developed underwater distributary channel microfacies, underdeveloped mouth bar, extensive sand sheet, and frequently alternate pre-delta and front deposition; 2) various facies belts are smoothly connected with each other without apparent slope gradient; and 3) depositional model has no three-layer structures like “Gilber delta”.