Abstract: The eastern depression is the only depression in which petroleum was found with good potential in the North Yellow Sea Basin. The time of petroleum accumulation in this depression will decide the strategy of petroleum exploration. Based on the studies of petroleum generation and expulsion history as well as sandstone inclusions in oil layers, the accumulation time for reservoirs in the eastern depression was discussed. Hydrocarbon was formed and expulsed from the middle Jurassic source rocks in Oligocene, and the sandstone inclusions in the Lower Cretaceous and the Upper Jurassic reservoirs were filled by oil in the early Miocene. Combined with the tectonic evolution of the basin, it was inferred that petroleum accumulated from the Late Oligocene to the Early Miocene in the eastern depression of the North Yellow Sea Basin.