Mg2B2O5w/6061Al matrix composites were fabricated through the powder metallurgy (PM) technique. The relationship among the parameters of ball milling, the powder characteristics, and the mechanical properties of hot extruded composites was investigated. The results showed that the reinforcement whisker accelerated the milling process by increasing the matrix deformation and enhancing the welding and the fracture of particles. And the mixing process was modified by using a higher milling speed, and suitable milling time, which resulted in the reduction of crystal size, improved homogeneity of the whisker distribution, as well as the enhanced tensile strengths of the hot extruded composites.