The invention provides a high-breathability lost foam coating prepared through cast waste resin sand and a preparing method of the high-breathability lost foam coating. The high-breathability lost foam coating comprises the cast waste resin sand, aluminum silicon series refractory aggregate, crystalline flake graphite, polystyrene resin particles, aluminum powder, an oxidizing agent, fluoride, carbon fibers, a suspending agent, a bonding agent, a surface active agent, a defoaming agent and water. The high-breathability lost foam coating comprises 100 parts of cast waste resin sand, 60-100 parts of aluminum silicon series refractory aggregate, 5-25 parts of crystalline flake graphite, 2-6 parts of polystyrene resin particle, 1-3 parts of aluminum powder, 2-10 parts of oxidizing agent, 1-5 parts of fluoride, 1-5 parts of carbon fiber, 3-10 parts of suspending agent, 5-15 parts of bonding agent, 0.2-0.5 part of surface active agent, 0.5-1.5 parts of defoaming agent and 80-120 parts of water. The cast waste resin sand is used as the main refractory material of the lost foam coating, casting wastes are effectively utilized, the green casting and circulation sustainable principles are met, the problems of carbon defects and contraction defects of the waste resin sand lost foam coating are solved, and good application prospects are achieved.