Abstract: A magnesium alloy composite material includes a magnesium alloy matrix, and a nanoparticle second phase material dispersed in the magnesium alloy matrix. The nanoparticle second phase material has an average particle size ranging from 1.0 nm to 100 nm. Preferably, the amount of the nanoparticle second phase material ranges from 0.05 wt % to 2.5 wt % based on total weight of the magnesium alloy composite material. With the addition of the nanoparticle second phase material to the magnesium alloy matrix, hardness can be increased to a relatively high level without significantly increasing density.