Hydrothermal hydrocarbons can occur in the ocean floor and in the continent.Experiments show that hydrothermal fluids catalyze the hydrocarbon generation in carbonates and sedimentary organic matter.The fluid inclusions of the ocean floor volcanic rocks and Pb,Sr and Nd isotopes of petroleum and organic matter also show that mantle fluids play an important role in the hydrocarbon generation.Recognition of hydrothermal hydrocarbon and its implications for the deep petroleum exploration are discussed.