The stability conditions of methane hydrate in a nannofossil-rich claystone column have been investigated using a temperature-controllable pressure vessel. Careful analyses of the reaction process of the experiments confirmed the formation of methane hydrate in sediments, then the pressure-temperature stability conditions of methane hydrate were recognized from the beginning and end of each hydrate dissociation step. The results show that the stability condition of methane hydrate at a given pressure in the test sediment column is shifted to the lower temperature field by 0.4°C and 1.5°C relative to those in sea water and pure water, respectively.