A casting method includes constructing a 3D model to add an inner wall compensation quantity, making a thin shell mold by a 3D printing machine, individually treating the thin shell mold by smooth processing, processing the thin shell mold by multi-layer impregnation slurry or gunite to make an outer shell mold, and to form a double-layer shell mold which includes the thin shell mold and the outer shell mold, processing the double-layer shell mold by sand filling and compressing, clearing the thin shell mold by a physical or chemical process, casting the outer shell mold to form a shaped article, and post processing the shaped article by shaking and sand clearing to form a product.