The invention discloses a coal-bed gas safe displacement extraction method based on a carbon dioxide phase-change fracturing device. The coal-bed gas safe displacement extraction method totally comprises the six steps that through a gas source system, carbon dioxide liquid is injected into a carbon dioxide fracturing device located outside a drilled hole; a high-pressure pressurizing injection mechanism and a large-flow medium-low-pressure injection mechanism are in series connection through a high-pressure hose and then connected with an injection hole of the carbon dioxide fracturing device,and the high-pressure pressurizing injection mechanism and the large-flow medium-low-pressure injection mechanism are connected with the gas source system; the carbon dioxide fracturing device and abag-type hole packer are pushed into the drilled hole by a hydraulic pushing machine, and the drilled hole is sealed; carbon dioxide liquid with the pressure being 60 MPa or above is injected into thecarbon dioxide fracturing device through the high-pressure pressurizing injection mechanism; and carbon dioxide gas or liquid with the pressure being the normal pressure of 10 MPa is injected into the carbon dioxide fracturing device through the gas source system and the large-flow medium-low-pressure injection mechanism. Safety is high, operation is convenient, and the gas extraction efficiencyis high.