The preparation of frozen sand molds for casting by CNC machining methods is an important basis for the realization of digital frozen sand green casting. This paper carries out a study on the optimization of robust parameters for CNC machining of frozen sand profiles at different mesh sizes and different water contents， to obtain the combination of cutting process parameters that has the least impact on dimensional accuracy. The dimensional accuracy of CNC machined frozen sand molds is more stable when the cutting speed is 188 m/min， the feed rate is 120 mm/s， the depth of cut is 3 mm and the cutting width is 8 mm. Research on optimization of parameters of multi-parameter coupled sand removal process for frozen sand type is carried out. Taking the sand discharge rate as an index， the influence laws of flow rate， target distance， pitch angle and caliber on the sand discharge effect under conditions of different cavity three-dimensional size are analyzed， and the combination of sand discharge process parameters is optimized. The flow rate is 30 L/min， target distance is 45 mm， pitch angle is 65°， and caliber is 2 mm. Coupled with the mechanical properties of frozen sand mold and sand discharge requirements， the optimized molding parameters are 100 mesh raw sand and 4% （mass fraction） water content. Through the test optimization， a complete frozen sand CNC machining sand discharge process parameter window can be obtained， thus achieving high precision and high efficiency of frozen sand CNC machining forming.