Abstract: In order to promote the study of exploration strategy in the east of Kalimantan, Indonesia, we studied in this paper the controlling factors over and the potential of oil and gas accumulation. Our results show that:(1) Eocene and Miocene deltaic and coal-bearing source rocks are widely distributed on the land and in the sea. The type, maturity and size of source rocks control the scales of hydrocarbon discoveries. The scale of discovery is larger in the sea comparing to that on land. Spatially, there is more gas in the central, and more oil in the north and south. (2) Source rocks and migration path are the two key factors to hydrocarbon accumulation and distribution. The difference of source and pathway system between the sea and the land is the reason to cause younger oil more in the sea area and older oil more on land area. (3)The "proximal thrust fault zone" in the Tarakan basin and the "buried basement hill belt" in the Barito Basin are the areas with good petroleum accumulation condition and larger exploration potential.