Abstract: The distribution of strata and reservoirs in the lower Paleozoic buried hill in Zhuanghai area is different in different well fields. The additional explorations of the buried hill are very important to identify the contributing factors of the complex reservoir space. The previous explanations of the reservoir formation, such as by the weathering crust, or those for fresh water of air, can not be applied here properly. The evidences of uniform temperature of inclusions and that of isotopes indicate that there are buried modifications in the studied area, and the main cause of the formation is the press-released water from the Tertiary. Modes of buried modifications are analyzed, and the three kinds of developmental modes of buried modifications are identified: the mode of supplying open-flow in the downward side; the mode of supplying contra-flow in the upward side; and the mode of directed influent supplying contra-flow in the bilateral bulge of anticline. The distribution of favorable reservoirs in the lower Paleozoic buried hill is controlled by the developmental modes of buried modifications. The stratum of the buried hill where the press-released water enters first of all usually is a favorable reservoir. On the other hand, the stratum of the buried hill where the press-released water passes out finally usually becomes a non-reservoir or a plugged zone. The results show that buried modifications can explain the formation of the complex reservoir space and the lower Paleozoic reservoirs and oil distribution models.