NOVELTY - Preparing natural gas doped with hydrogen, involves pulverizing biomass material, adding the pretreated biomass material and hydrogen-producing inoculum to reactor, purifying and extracting methane, carbon dioxide, hydrogen sulfide, and water mixed gas, obtaining pure hydrogen, feeding hydrogen residue to subsequent methane reactor, feeding the mixture of the hydrogen residue and methane inoculum to anaerobic methane reactor, subjecting methane residue to environmentally-friendly treatment, and mixing pure hydrogen and pure methane.    USE - The method is useful for preparing natural gas doped with hydrogen.    ADVANTAGE - The method is simple, convenient to perform, easy to control hydrogen doping ratio, and suitable for processing and generating clean energy sources by biomass resources, consumes less fossil energy, produces hydrogen and methane at same time, and reduces production cost of hydrogen. The anaerobic fermentation and methane production is performed at normal pressure and normal pressure.    DETAILED DESCRIPTION - Method of preparing natural gas doped with hydrogen by biomass material, involves (a) pretreating biomass material by removing impurities from biomass material, and pulverizing the biomass material, (b) adding the pretreated biomass material and hydrogen-producing inoculum to anaerobic hydrogen production reactor, controlling the pH of anaerobic hydrogen production fermentation to 4.5-6.5, producing hydrogen and carbon dioxide from hydrolysis action of hydrogen production fungus from the biomass material, producing small amount of hydrogen sulfide, purifying and extracting methane, carbon dioxide, hydrogen sulfide, and water mixed gas by desulfuration, decarburization and dehydration steps, obtaining pure hydrogen, feeding hydrogen residue to subsequent methane reactor, and controlling pH of anaerobic methane production fermentation, (c) feeding the mixture of the hydrogen residue and methane inoculum to anaerobic methane reactor, controlling pH of the anaerobic methane production fermentation, purifying and extracting the CH4, CO2, H2S and H2O mixed gas by desulfuration, decarburization and dehydration steps, obtaining pure hydrogen, and subjecting methane residue to fertilizer utilization or environmentally-friendly treatment, and (d) mixing pure hydrogen and pure methane based on required hydrogen doping ratio to obtain the natural gas doped with hydrogen.