Abstract: Taken the composites of TiB₂/Al and TiB₂+Mg₂Si/Al Al-matrix as examples in this paper, the in-situ fabrication techniques of Al-matrix composites reinforced with single or hybrid particles and the advantages of hybrid reinforcement are investigated. The salt-metal reaction route and melting process were combined to fabricate 5vol% TiB₂+10% Mg₂Si/Al composites successfully. Microstructure analysis and performance testing were carried out, and the results showed that, the TiB₂ particles can act as good heterogeneous nucleation site for Mg₂Si phase, which leads to the refinement and uniform distribution of Mg₂Si. The Mg₂Si eutectic phase is refined from over 50 μm to under 10 μm. TiB₂ particles gathered along the grain boundary are broken up by Mg₂Si phase, and TiB₂ particles are uniformly distributed. The mutual refinement of TiB₂ particles and Mg₂Si phase is discovered. Compared with TiB₂/Al composite, the yield stress and ultimate tensile strength of TiB₂+Mg₂Si/Al composite are improved by 88% and 45%, respectively.