A preliminary research of the benthic Foraminifera from Integrated Ocean Drilling Program (IODP) Expedition 311 has been carried out for the purpose of better understanding their stable carbon isotopic response to the marine gas hydrate geo-system. SEM photographs and stable oxygen isotopes of the species Uvigerina peregrina and Bulimina mexicana indicated that diagenesis and authigenic carbonate precipitation had little effect on Foraminifera. Uvigerina peregrina and Bulimina mexicana collected from the sediments in seepage Site U1328 and in adjacent non-seepage Site U1327 exhibited a distinct negative δ¹³C excursion with values of U. peregrina -0.67‰～-2.75‰ PDB, B. mexicana -0.51‰～-1.52‰ PDB in Site U1327 and U. peregrina-0.72‰～-2.71‰ PDB, B.mexicana -0.58‰～-1.45‰ PDB in Site U1328 respectively. The formation of distinct stable carbon isotopic excursions of benthic Foraminifera could be most likely interpreted by the involvement of both anaerobic oxidation of methane (AOM) and food sources in sediments. The distinct negative carbon isotopic excursion of benthic Foraminifera thus could be believed as one of indicators to recognize the marine gas hydrate geo-system.