The surfacing welding has been widely utilized in the industrial equipment manufacturing and repairs. The wear properties of surfacing alloys have an important effect on the whole performance of repaired components. The solution treatment (T4) and solution treatment followed by aging (T6) effects on the dry sliding wear behavior of surfacing AZ91 magnesium alloys with tungsten inert gas welding were investigated in this work. The results demonstrated that the surfacing alloy without treatment exhibited poor wear resistance, due to the massive intermetallic β-phases (Mg17Al12). These phases were believed to produce stress concentrations in the particle-to-matrix interface and tended to generate cracks during friction. The T4 alloy had more improved wear resistance than the as-received alloy. The T6 treatment improved the wear resistance further, resulting from the high density dispersed fine β-phase precipitation in the α-Mg matrix, which enhanced the alloy strength and hardness and decreased the subsurface metal deformation degree caused by friction.