The hydrocarbon is mainly distributed in shallow water delta system of N1 mL in the Huanghekou sag. The hydrocarbon distribution and accumulation are analyzed according to sequence-structure herein. The lower member of Minghuazhen Formation is recognized as 3 long-term cycles and 8 middle-term cycles with high resolution sequence stratigraphy in Neogene. The early phase of ascending half cycles and middle-late phase of descending half cycles form sandbodies development favorable position are the main position of hydrocarbon distribution. Structure setting controls the direction of hydrocarbon migration, and positive structure zones are favorable areas of petroleum migration and accumulation. The faults of connecting deep and shallow strata are the main pathway of petroleum migrating to Neogene in the vertical direction. And, the late-stage faults adjust and distribute hydrocarbon. The sequence-structure controls the hydrocarbon accumulation layer and enrichment degree, and the good matching relation between faults (especially oil-migrating faults) and reservoir-seal assemblage is the main reason accounting for high hydrocarbon accumulation. The sequence-structure determine the effectiveness of the Neogene traps, and formed lithologic-structure, structure-lithologic and lithologic hydrocarbon reservoir.