Provided is a sand mold line forming and laying method. Firstly, a printing plane is meshed, a layered sand mold three-dimensional mesh model is built, mesh filling information is generated, then meshes are laid layer by layer, the printing plane conducts transverse scanning movement when each layer of mesh is laid, and blanking nozzles which are longitudinally arranged in columns are used for filling the corresponding meshes with molding sand or auxiliary molding sand according to the mesh filling information. The scanning printing mode from line to face is adopted, the meshes can be filled by dynamically selecting materials, the forming speed of a sand mold is increased, and the method is suitable for production and manufacturing of large-scale casting sand molds.