The invention discloses an experimental device for simulating stratum deformation in an NGH (natural gas hydrate) exploiting process. The experimental device comprises a reaction kettle, an axial pressure piston, a kettle outer jacket, an injection system, an axial pressure control system, an ambient pressure control system and an output system. The invention further discloses an experimental method for simulating the stratum deformation in the NGH exploiting process by adopting the experimental device. The method comprises the following steps: in a hydrate generation process, ice powder particles in proper particle size are prepared through an ice powder production system, ice powder is mixed with dried submarine sediment particles, and hydrate samples with different occurrence forms and different saturation degrees can be generated. Axial deformation quantity of a sample cavity as well as gas output, water output and sand output data is calculated in an exploiting experiment. According to the experimental device and the experimental method, the influence of the hydrate samples under various geological conditions and with different occurrence forms on the stratum deformation in a decomposition process can be simulated, basic data of the influence of decomposition of NGH on the stratum deformation are obtained, and the experimental foundation and basis are provided for real NGH exploiting.