The wear of blade spreader in powder spreading process in Additive Manufacturing is explored by experiment and numerical simulation using Discrete Element Method. The results identify a new mechanism for the wear of blade spreader, i.e. transient jamming of particles. Significant wear of blade spreader could be observed when the gap between the spreader and base is less than 2 times of particle diameter D90. The wear depth is more sensitive to particle interlocking than particle cohesion. Large wear depth or a long scratch could be induced by bumps or spatters on the base. The wear mainly occurs at the front bottom surface of the blade spreader. A simple method is proposed to reduce the wear of the blade spreader.