Boundary separation Approaching Rapid Casting is present. In this method, the 3-D CAD model of casting mould is sliced with certain thickness, and the 2-D profile of every slice is converted into the NC code automatically by computer. For case study, taking coated sand as material, casting moulds of propeller was made rapidly by self-developed laser rapid prototyping system. The casting test showed that this method can produce good quality parts. Boundary separation Approaching Rapid Casting with the characteristics of high production efficiency can cast products with complex cured surfaces in multi-variety and small batch, and it is a great significance in reducing the cost and shortening the cycle of new products development.