Abstract: Grinding is the result of the combined action of impact and abrasion， but the single abrasion effect wasn't systematically studied in the previous studies. Two common minerals pyrite and pyrrhotite were taken as research objects. The particle size distribution characteristics and rules of grinding products under the action of grinding were studied using the methods of relative grindability and grinding kinetics analysis， so as to preliminarily discuss the grinding characteristics of grinding machine in the falling state. The results showed that under the same conditions， the finer the particle size of mineral feeding， the more obvious the change of grinding product particle size with the grinding time. Pyrite will obtain a higher grinding fineness in a short time， but with the extension of the grinding time， the change of grinding fineness of pyrrhotite is more obvious， and the influence of grinding time on pyrrhotite is greater. The particle size distribution characteristics of the grinding products have a good fit for the first-order linear dynamic model of grinding. Based on the test results， it can provide a theoretical basis for the follow-up study of the motion law and grinding characteristics of the grinding media under the condition of abrasion.

Key words: Grinding action, Relative grindability, Particle size analysis, Grinding kinetics