NOVELTY - Preparing natural biogas using organic matter comprises: adding processed raw material from preprocessing device (1) and inoculum into anaerobic dry fermentation device (2), and performing anaerobic fermentation to generate methane gas; pumping a liquid having low carbon dioxide content from the decarbonization device (4), achieving absorption of carbon dioxide by methane gas; pumping the liquid to flow into the decarbonization device, so as to make the liquid to recover the carbon dioxide absorption capacity; and discharging the waste gas from the decarbonization device.    USE - The method is useful for preparing natural biogas using organic matter.    ADVANTAGE - The method is environmental-friendly, multi-functional, fully utilizes the resources, and generates clean gas.    DETAILED DESCRIPTION - Preparing natural biogas using organic matter comprises: adding processed raw material from preprocessing device (1) and inoculum into anaerobic dry fermentation device (2), and performing anaerobic fermentation to generate methane gas; setting an liquid spraying device (3) on the upper space of the anaerobic dry fermentation device, pumping a liquid having low carbon dioxide content from the decarbonization device (4) via spray pump (5), achieving absorption of carbon dioxide by methane gas, and improving the mass transfer and heat transfer effect within the anaerobic dry fermentation system; after carbon dioxide absorption, pumping the liquid from the bottom of the anaerobic dry fermentation device into the decarbonization device via the liquid circulation pump, so as to make the liquid to recover the carbon dioxide absorption capacity; discharging the waste gas from the decarbonization device, and treating in the purifying device.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of the device for preparing natural biogas using organic matter (Drawing includes non-English language text).    Pre-processing device (1)    Anaerobic dry fermentation device (2)    Liquid spraying device (3)    Decarbonization device (4)    Spray pump (5)