The utility model relates to a testing device for simulating CO2 injection for fire prevention and extinguishment in a coal mine goaf and designs the testing device for simulating CO2 injection for fire extinguishment in the coal mine goaf for the condition of severe coal spontaneous combustion during coal mine extraction and facts that the coal spontaneous combustion elimination difficulty is high and fire extinguishment is not easy. A mechanical structure is adopted, and the CO2 fire prevention and extinguishment simulating law is obtained through heating, temperature measurement, temperature control, air inlet, air return, CO2 input, CO2 control, sampling, analysis and measurement by a gas chromatograph and operation by an information computer, so that the device can be better used for fire extinguishment in a coal mine field. The device is advanced in design and reasonable in structure, integrates field simulation, information acquisition and processing functions, can obtain CO2 fire prevention and extinguishment data accurately and is an ideal testing device for simulating CO2 injection for fire prevention and extinguishment in the coal mine goaf.