Abstract: The friction and wear behavior of fly ash particles reinforced ZL109 composites prepared by the squeeze-casting method were investigated under various conditions. Under the lower loads and at the lower sliding speeds,the wear resistance of the MMCs is superior evidently to that of the Al matrix, and increases with the volume fraction of fly ash particles. The friction coefficient is steadily lower than that of Al matrix. The improvement of the wear resistance of the MMCs decreases under the higher loads and at the higher sliding speeds compared with Al matrix. But the friction coefficient of the MMCs could still keep a lower value. The reason is that the wear mechanisms in the MMCs have been transformed with increasing load and sliding speed. The transformation of wear mechanisms in MMCs was also investigated in the paper.