The invention discloses a method for preparing natural gas by carbon dioxide sectionalized methanation. The method comprises the following steps 1) and 3) or 2) and 3): dividing H2 into at least 3 streams, respectively inputting into 3 series-connected methanators, dividing CO2 into at least 3 streams, respectively inputting into the 3 series-connected methanators, and carrying out methanation; 2) dividing CO2 into at least 3 streams, respectively inputting into 3 series-connected methanators, dividing H2 into at least 3 streams, respectively inputting into the 3 series-connected methanators, and carrying out methanation; and 3) inputting outlet gas of the methanators into at least 2 series-connected methanators, and carrying out methanation, wherein the outlet gas of the methanators is the natural gas product. The acting reactants and the reaction products (CH4 and H2O) of the previous reaction are controlled by reaction, thereby preventing the added vapor for temperature control on the influence of the methanation balance in the traditional methanation technique.