The invention discloses a grass suppression straw biomass-base degradable mulching film and application. A method for preparing the grass suppression straw biomass-base degradable mulching film includes S1, biologically pretreating straw, to be more specific, compounding phanerochaete chrysosporium and streptomyces rochei, then inoculating the phanerochaete chrysosporium and the streptomyces rochei on the straw, adjusting carbon-nitrogen ratios and moisture contents of material systems and carrying out aerobic fermentation; S2, softening, disassembling and separating straw fibers, to be ore specific, softening the pretreated straw fibers and disassembling the pretreated straw fibers until the fiber lengths are 0.5-2 cm; S3, forming straw biomass-base mulching films, to be more specific, uniformly mixing the straw fibers, wood pulp, methyl celluloses, sodium alginate, gelatin, polyamide epichlorohydrin resin, alkyl ketene dimmers, polyacrylamide, glycerol, alkenyl succinic anhydride grafted starch adhesive and biochar with one another, and carrying out vacuum dehydration, squeezing, drying and forming to obtain the grass suppression straw biomass-base degradable mulching film. The grass suppression straw biomass-base degradable mulching film can be applied to the field of paddy rice seedling raising.