The invention discloses a method for preparing an elastomer based on azidized modified nitrocellulose microspheres. The method comprises the following steps: preparing terminated alkynyl PEG; then dissolving the terminated alkynyl PEG in tetrahydrofuran (THF); adding a plasticizer to NC-N3 microspheres, and then adding the material to the above THF solution in which the terminated alkynyl PEG is dissolved, and stirring the materials to obtain an adhesive mixed system H; adding a catalyst cuprous halide to the mixed system H under N2 protection and stirring conditions, and stirring the materials uniformly; casting the adhesive mixed system H into a teflon mold and curing the material at room temperature for 7 days to obtain an NC-N3 microsphere-based elastomer film. The method is based on the condition that a propellant adhesive system is introduced in the form of microspheres without change of NC, and invents the simple preparation method based on the NC-N3 microsphere elastomer, and the prepared elastomer film has better mechanical properties, and has great application potential for the gunpowder adhesive systems such as the propellant.