Abstract: The influence of the abrasive size, rotation speed and load on the wear properties of 45# steel was investigated on grinding abrasion testing machine by using quadratic orthogonal rotational regression method with alfalfa powder, and the best conditions of the wear test was determined. Under this condition, authors made a further study on the soft abrasive wear behavior of alfalfa powder to 45# steel and observed the worn surface morphology of the metals by a scanning electron microscope (SEM). The results showed that the influence factors of the wear properties were rotation speed, the abrasive size and load in the order of importance, and the wear properties of 45# steel was better in subcritical quenching than in annealing; The wear of 45# steel was caused by the hard and soft abrasive formed by alfalfa powder.The soft abrasive wear of annealing 45# steel was dominated by the fatigue wear, while the wear of quenching 45# steel was dominated by the micro-cutting wear.