Abstract: Base on the understanding that the Upper Cretaceous Sarvak reservoir of Azadegan oilfield in Iran is an unsteady state reservoir with an inclined oil?water contact, this paper studies the accumulation features of the reservoir using the data of 3D seismic, core analysis and actual drilling. The result shows that the reservoir was influenced by Late Cretaceous Alpine tectonic movement and the paleotraps formed with the features of higher in the north and lower in the south. The reservoir received the charging of hydrocarbons generated in Kazhidumi source rocks in the eastern Dezful depression of the oilfield in Miocene, and thus the ancient reservoirs formed. Miocene Zagros orogeny resulted in the structural inversion of the paleotraps that evoluted into the current structural configuration of two highs both in the south and north, and higher in the south and lower in the north. Because this change broke the dynamic balance of the paleotraps and the tectonic movement didn’t impact the overlying cap rocks, the secondary migration from the paleotraps in the north to the secondary traps in the south occured in the blocked accumulates. The reservoirs are still in the unsteady state of the early modulating stage, that means a steady horizontal oil?water contact is noted in the northern paleotraps and a significant incline uplifting oil?water contact exists in the southern secondary traps