Abstract: Carbon nanotubes(CNTs) and Ti₃AlC₂ reinforced phase was surface modified by electroless copper plating. The CNTs-Ti₃AlC₂/AZ91D composites was prepared by hot pressing (HP) sintering. The microstructure, mechanical properties and strengthening mechanism of the CNTs-Ti₃AlC₂/AZ91D composites were studied.The results indicate that the main physical phases in the CNTs-Ti₃AlC₂/AZ91D composite are CNTs, Ti₃AlC₂, Mg and Al₁₂Mg₁₇, and the reinforced phase is uniformly distributed in the matrix. There is a U phase (MgAlCu) at the interface between the reinforced phase and the matrix, which can make the interface of the two well combined. When the reinforced phase content is CNTs (1wt%) and Ti₃AlC₂ (25wt%), compared with magnesium alloyAZ91D, the elasticity modulus, tensile strength, yield strength and elongation of the CNTs-Ti₃AlC₂/AZ91D composites are increased by 120.30%, 25.72%, 126.50% and 36.84%, respectively, and the flexural strength and compression strength are 337.92 MPa and 436.27 MPa. The fracture mode of the CNTs-Ti₃AlC₂/AZ91D composites is brittle fracture, and the strengthening mechanism is mainly thermal mismatch strengthening, Orowan strengthening and fine grain strengthening.