The invention discloses an experimental device and a method for carbon dioxide replacement exploitation of gas hydrate. The experimental device comprises a one-dimensional model, a gas supply unit, a working solution supply unit, an axial compression control unit, a back pressure control unit and an environment control unit. Each unit is respectively provided with a sensor connected to a data processing unit. The one-dimensional model is arranged in the environment control unit. The inside of the one-dimensional model is a sealed simulation cavity. The upper part of the one-dimensional model is provided with a gas and solution inlet, a gas and solution outlet and an axial compression solution inlet. A gas output pipeline of the gas supply unit is communicated with the gas and solution inlet after being connected with a working solution output pipeline of the working solution supply unit. A back pressure acquisition pipeline is communicated with the gas and solution outlet. The axial compression control unit is connected with the axial compression solution inlet. The one-dimensional model is also provided with a vacuum-pumping interface. The invention can really simulate the external environment to carry out simulation exploitation of carbon dioxide replacement of the gas hydrate, and can provide guidance for the carbon dioxide replacement exploitation of the gas hydrate.