Abstract: Block Ⅲ of Cuba is a contractual block of risk exploratory development in the foreland basins in Cuba. It is located in the southwest of Mexico Gulf and registered by SINOPEC. Petroleum geology of this block was analyzed synthetically, its hydrocarbon accumulation conditions and exploration potential was evaluated and the favorable oil/gas exploration zone was predicted combining the database of drilling, geophysical exploration and geochemistry in view of current status of the studies. Source rocks (Upper Jurassic-Lower Cretaceous marlite and argillaceous limestone, and Mid-Lower Jurassic shale) occurred in Block Ⅲ, and reservoirs were mainly composed of micrite limestone, limestone and sand-conglomerate rocks. The early traps were almost destroyed during orogenic phase and effective .traps formed mainly in Paleogene including anticlines, fault nose, faulted blocks, and lithologic traps, : from which it was speculated that several assembling types of the oil-generating strata, reservoir strata and overlying strata developed. Analysis of regional correlation and the drilling information showed that the foreland thrust belt in this area was the most favorable exploration area, and the thick tertiary strata occurred in the north margin of south basin was predicted to be the favorable potential area.