Slurry erosion of polystyrene were studied by a jet apparatus, and erosion behavior was investigated by considering the effect of flow on the impact behavior of slurry particles on the specimen. Erosion rate differed greatly at different positions on the specimen, due to differences in impact velocity and angle of the slurry particles. When the slurry jet impacted a specimen set perpendicular to the jet axis, assuming stagnation flow, the distribution of impact velocity, angle and striking efficiency could be numerically calculated. The distribution of specimen erosion depth was estimated on the basis of calculation, and these results agreed approximately with experimental results. It was concluded that an understanding of the effect of fluid flow on the behavior of slurry particles is important to make clear the slurry erosion damage. © By THE SOCIETY OF CHEMICAL ENGINEERS, JAPAN.