Mud core moulding sand for casting is prepared by the following raw materials including, by weight, 200-240 parts of quartz sand, 30-35 parts of attapulgite, 50-55 parts of perlite, 30-35 parts of sepiolite, 12-17 parts of glass fibers, 30-40 parts of alumina, 2-3 parts of aminopropyltriethoxysilane, 10-12 parts of cellulose gum, 1-2 parts of stearoyl-rac-glycerol, 2-3 parts of epoxidized triglyceride and water in proper amount. By using quartz sand, attapulgite and perlite and through calcining, rich holes are provided, and air permeability is good; by combining with grinding of sepiolite, alumina, cellulose gum and the like, the moulding sand is enabled to have excellent cohesiveness, plasticity and thermal stability; by adding the glass fibers, strength of the moulding sand is enabled to be greatly improved. The mud core moulding sand for casting has the advantages of high dry and wet strength, good air permeability, low gas evolution, quickness in calcining and curing and low mud core scrappage.