The invention provides a preparation process and a casting mould for a cast product based on the 3D printing technology, and belongs to the technical field of mould processing. The preparation process comprises the following steps: A, designing a casting mould model by utilizing a three-dimensional software, converting the casting mould model into a STL data format, leading the STL data format into a slicing software to carry out slicing processing, enabling a thickness of a laminate sheet to be 0.01-2mm, and enabling the wall thickness of the casting mould model to be greater than or equal to 0.5mm, thereby obtaining three-dimensional model data of the casting mould; B, leading the three-dimensional model data, obtained in the step A, of the casting mould into 3D printing equipment, carrying out printing and molding, thereby obtaining the casting mould; and C, injecting a fluid raw material into a mould cavity of the casting mould in the step B, thereby obtaining the cast product. The casting mould comprises mould cavity surrounding boards, and a mould cavity defined by the mould cavity surrounding boards, wherein an injection hole and an overflow hole are formed in the top of each mould cavity surrounding board. The preparation process and the casting mould has the advantages such as high processing precision, less material consumption, high production efficiency, simple manufacturing processes, low production cost and the like.