The invention discloses a starch-based composite mulching film with good water resistance performance. The starch-based composite mulching film comprises, by weight, 64-70 parts of dry-basis corn starch, 23-26 parts of ethyl alcohol, 11-15 parts of monochloroacetic acid, 14-16 parts of silicon dioxide, 0.08-0.1 part of epoxy chloropropane, 60-80 parts of dimethyl formamide, 4-5 parts of silicone, 4-5 parts of adhesives, 2-3 parts of brown seaweed polysaccharide, 0.05-0.08 part of glutaraldehyde, 4-5 parts of polyacrylonitrile-based carbon fibers, 3-5 parts of dioctyl phthalate, 0.2-0.3 part of antioxygen BHT, appropriate parts of 85% of ethanol solution and appropriate parts of deionized water. The degradable agricultural mulching film can be completely decomposed by microorganisms, does not influence environment, and has excellent performance and high water, aging and impact resistance; film forming property is excellent, production efficiency is high, and cost is reduced.