Abstract: Diamond wire saw is widely used in the field of chip processing of hard and brittle materials such as monocrystalline silicon and sapphire. With the large size of the chip and the fine line of the sawing wire, the kerf is more and more "deep and narrow" in the sawing process, and the cutting fluid plays a full role in the sawing process, which has a great impact on the quality of the slice. Based on the numerical simulation of computational fluid dynamics, the cutting fluid flow field in the kerf of diamond wire saw was analyzed and studied by establishing the CFD kerf model. The simulation analysis found that: in the small size kerf, with the increase of wire speed to more than 25m/s, the cutting fluid can more fully enter the kerf, after the sawing wire and the workpiece contact area and non-contact area filled with liquid, the fluid pressure in the contact area is about 0.179MPa, the fluid pressure in the non-contact area is about 0.159MPa; The reduction of the viscosity and surface tension of the cutting fluid in a certain range is conducive to ensuring the relative saturation and stability of the cutting fluid in the kerf, and the pressure distribution of the cutting fluid in the kerf is more stable.