Abstract: Abrasive wear caused by the alfalfa powder is the main reason for the failing of the key parts of the feed circular mould pellet machine.The influence of the load,rotation speed and granularity on the tribological properties of 45~# steel and HT200 gray cast iron sliding against alfalfa powder were investigated on an ML-100 test rig by using orthogonal design. The worn surface morphology of the metals was observed on a scanning electron microscope(SEM).The results showed that the influence factors of the wear properties are rotation speed,granularity and load in the order of importance,and the wear of the metals was caused by the hard and soft abrasive formed by alfalfa powder.When running against hard abrasive,the worn surface of the 45~# steel was characterized by the micro-cutting wear,while it was dominated by plastic deformation and fatigue wear in the case of soft abrasive.For the HT200 gray cast iron,the wear was caused mainly by the brittle flake.