Natural gas hydrate is one of the most important potential energy sources distributing in the seabed and continental permafrost; at the same time

the dissociation of hydrate in hydrates bearing layers is a triggering factor of global climate change and geologic hazards. The method and apparatus for formation sample is a basic issue for researching on hydrates-bearing sediments(HBS)

which require homogeneity of the sample according with in-situ formation mode as soon as possible. Most marine hadrate formed in diffusion system

which means the gas transfered to the hydrate occur zone by diffusion in water and formed hydrate.Gas-bearing water is moved in cycles by constant-flow pump in this method and apparatus; and gas solubility in water is enlarged through stirred by magnetic stirring apparatus; soil sample could be saturated with gas-bearing water in short time; and then reduce the temperature of soil sample

Gas dissolved in water associates with water to form hydrate filling in the pore of soil sample equably. The experiments show that 1 day is spent to form the hydrates-bearing sediments used by silt and CO2 sample. Homogeneity is testified through observing and testing water-contents of different positions in formed sample. Thereby

heterogeneity caused by hydrate distribution in pore of sample and cost time too long is dissolved well; technological basis is provided for physico- mechanical experiments of hydrates bearing sediments.