Abstract: Abstract: Abrasive flow machining method is a new precision processing method. Unlike the traditonal mechanical processing, the biggest feature of this technology is its polishing liquid. Because of the rheological properties of the polishing liquid, it can enter into any complex and tiny flow channels without limitation. In addition, according to the size and structure of the machined parts, the suitable polishing fluid can be simply and effectively configured. In the abrasive flow machining process, the inlet velocity is the main parameter affecting the processing efficiency and accuracy of the abrasive flow. Therefore, the inlet velocity is selected as the processing parameter to study the processing effect of the abrasive flow on the part. At present, most of the research content about abrasive flow processing is mainly focused on the machine parameters and abrasive configuration, while the particles decisive role in the whole process was ignoring. The essence of abrasive flow processing is the shear, collision, and friction between the innumerable particles and the processed surface,,so it is great significance to study the distribution and mechanical properties of particles. Based on the above background, the micro-component dispensing head is selected as the simulation and test object in this paper. With the abrasive flow machining technology and the combination of CFD ( computational fluid dynamics) and DEM (discrete element method), the fluid simulation software FLUENT was used to perform the numerical analysis of the abrasive flow machining process, and the distribution of fluids and particles during processing were discussed, the distribution of fluids and particles under different inlet velocity conditions was compared and analyzed, the micro-cutting behavior of the abrasive flow machining was revealed. The collision model of the particles impact the processed surface was established. The effect of the abrasive flow on processed surface and the material removal mechanism were clarified. Numerical simulations showed that, with the increase of the inlet velocity, the effects of fluids and particles on the processed surface were enhanced, the friction and collision between the particles and the surface were severer, more kinetic energy of the particles was converted into cutting energy, and the removal rate of the material was improved. The collision model showed that the removal of the surface material was achieved by continuous impact and shear of the particles. The NT100 grating measuring instrument and scanning electron microscope were used to detect the surface topography after the abrasive flow processing. The test results showed that the surface roughness decreased from 2.03μm to 0.65μm., the surface roughness was significantly lower than that before processing, and the surface quality was obviously improved. The study provides a reference for further research on abrasive flow processing and micro-cutting.