Abstract: Abstract: During the course of mold manufacture, lots of structural surfaces are involved, which are of complicated structure and tiny scale. Owing to the special profile of a structural surface, its finishing cannot be realized by the traditional method; so a softness abrasive flow ultraprecision machining method is proposed for mold structural surface finishing. Because of the weak viscosity of softness abrasive flow, it could develop turbulent flow easier than viscous fluids. The best finishing result can be obtained with the turbulent softness abrasive flow, so the flow pattern recognition of softness abrasive flow is necessary. Taking the structural surface of vehicle mold as the study object, a realizable k-ε double-equation turbulent model is used to describe a softness abrasive flow field. Based on the finite element analysis method, computational fluid dynamics (CFD) software was used to simulate the softness abrasive flow field. With the numerical simulation, distributions of dynamic pressure, velocity vector, and turbulent dissipation rate of the softness abrasive flow field were obtained; and the evolutionary process of the softness abrasive flow was showed by simulating different moments of particle motion trails, and the feasibility of a softness abrasive flow finishing method has been proved by these simulation results. Based on the similarity theory, a model of flow passage which was made of plexiglass was designed, three typical areas of the flow passage were selected for measuring the characteristics of the flow field, and the measurement platform of the softness abrasive flow field was constructed by using particle image velocimetry (PIV) technology. With the measurement platform, distribution of particle motion, velocity vector, and flow field vorticity were derived. From the particle motions, it was shown that the particles in the flow field were moving irregularly, particles can collide with the surface randomly, and the removal finishing can be realized; particle motion trails are observed from the velocity vector distribution, it was shown that particle trails in the flow field were votex, which was according to the features of turbulence, and this was conducive to the mold structural surface finishing. The vorticity distribution of the flow field illustrates that the softness abrasive flow has high vorticity energy, and it was helpful for increasing materials removal. Contrasting with simulation and measurement results, the softness abrasive flow field in this situation is turbulent, and the ultraprecision machining of mold structural surface can be realized by the softness abrasive flow in this state. A finishing platform which oriented to mold the structural surface was constructed, with the turbulent softness abrasive flow, the finishing experiment which was designed to mold the structural surface was carried out. The experiment results showed that SAF method can improve the surface quality of a mold structural surface without changing the morphology, and the machined roughness of a mold structural surface can be reduced to 27 μm. Experimental results have demonstrated the effectiveness of a softness abrasive flow finishing method.