Disclosed is an experimental device for studying the sediment yield behavior and the radial deformation of porous media during the exploitation of natural gas hydrates, comprising a high-pressure reactor, a hydrate sample chamber, a simulated wellbore, a deformation measurement unit, an ambient temperature control unit, an outlet control unit, an inlet control unit and a data processing unit. Further disclosed is a method using the above-mentioned experimental device to carry out experiments. The experimental device and method according to the present invention can conveniently measure the deformation of the porous media during the decomposition of the hydrates and simulate the sediment producing situation in the wellbore, can simulate the sediment yield problem during the exploitation of natural gas hydrates as well as the gas-liquid-solid flowing problem in the wellbore during the exploitation of natural gas hydrates, and can accurately obtain the gas-solid-liquid three-phase yields in real time during the decomposition of natural gas hydrates. Being simple to operate and easy to control, and suitable for various sizes and shapes of reactors, it can provide basic experimental data and a theoretical basis for the technologies of hydrate exploitation.