The invention discloses high-ventilation collapse-easy core sand for vehicle casting and a preparation method thereof. The high-ventilation collapse-easy core sand is prepared by the following raw materials in parts by weight: 140-150 of limestone sand, 20-30 of electric-molten ceramsite sand, 16-20 of menaccanite, 10-15 of hollow brick slag, 12-14 of vanadium extracting tailing, 14-18 of green pyroxenite, 8-10 of coal water slurry slag, 15-20 of Soochow soil, 8-12 of salt gypsum, 8-10 of water glass, 5-7 of ammonium sulfate, 2-4 of niobium diselenide, 3-5 of gamma-polyglutamic acid, 1-2 of ethylene glycol diacetate and the like. The core sand uses such raw materials as Soochow soil, salt gypsum, water glass, gamma-polyglutamic acid, starch sodium octenylsuccinate and carboxymethylinulin natrium as adhesive, is low in ventilation quantity and high in green compression strength in the casting process, and is excellent in collapsibility; the added niobium diselenide, green pyroxenite and the like form a compound under high temperature with the adhesive, so that the early melting of the adhesive is prevented, and the residual strength of the core sand is improved; and the added ammonium sulfate and the like are heated to decompose to release such gas as nitrogen and water, so that the collapse effect is excellent.