Natural gas hydrate has huge reserves in the world，which is considered to be one of the most promising unconventional energy to replace the conventional energy in the future. At home and abroad, there are lots of researches on gas hydrate. However, it is difficult to achieve original gas hydrate samples for its special properties. At present, the method of preparation natural gas hydrate in laboratory is widely adopted for hydrate research. This paper focused on the existing problem for the synthesis of natural gas hydrate in porous media of the traditional method, namely, the porous medium blockage caused by the expansion of gas hydrate synthesis and provided a new method of natural gas hydrate samples synthesis in a dynamic environment. That is the method of compound natural gas hydrate by gas and deionized water in the process of circulation. The results showed that the new method could compound gas hydrate with higher saturation in porous media with 20% - 30%.