The invention discloses a modified degradable film material preparation method which includes the steps: dissolving alkali lignin in deionized water, adding pretreated expanded vermiculite after heating and stirring, continuing stirring, filtering and drying mixture to obtain lignin doped modified expanded vermiculite, placing the lignin doped modified expanded vermiculite into a tubular furnace and carbonizing the lignin doped modified expanded vermiculite in argon protection; adding deionized water into hexadecyl trimethyl ammonium bromide, sufficiently stirring and dissolving the deionizedwater and the hexadecyl trimethyl ammonium bromide, mixing solution with sodium-based montmorillonite turbid liquid, performing standing and suction filtration after stirring, flushing the mixture with deionized water and ethanol, and drying, grinding and sieving the mixture to obtain organic modified montmorillonite; mixing cassava starch solution, nano-material solution, chitosan solution, polyvinyl alcohol solution, carbon hybridization modified expanded vermiculite and the organic modified montmorillonite, adding anhydrous ethanol, glycerol and glutaraldehyde, coating a glass plate with the mixture after suction filtration, drying the mixture into a film, removing the film, and performing equalization treatment in a dryer containing saturated NaBr solution to obtain a degradable film material.