Abstract: By changing the mass fraction of Ti-C-Al preform and AZ91D magnesium alloy, TiC/AZ91D magnesium matrix composites were prepared by in-situ synthesis method at 780 ℃. The effects of preform content on the microstructure evolution and friction and wear properties of the composites were studied. The experimental results show that Al₃Ti and TiC appear in the microstructure of AZ91D magnesium alloy composites with the addition of Ti-C-Al preform. The number of Al₃Ti and TiC increases with the increase of the preform content, but the total amount of Al₃Ti and TiC in the alloys with20wt% and 30wt% of Ti-C-Al preform is not different. The results of friction and wear performance test show that the volume wear rate decreases first and then increases with the increase of preform content, and the relationship between wear rate and hardness is inversely related. The sample with 20wt% preform content has the lowest volume wear rate, the lowest friction coefficient and the highest hardness. Abrasive wear is the main form of the composites, the wear feature is furrow.