In-situ magnesium silicide/aluminum (Mg₂Si/Al) composites were fabricated by laser deposition. A dynamic model of in-situ Mg₂Si/Al composites was established. The laser power (system temperature), Mg-rich layer thickness, Si particle size, and Al content were identified as the main factors affecting the reaction rate and degree. Results show that increasing the laser power (system temperature) and reducing the Mg-rich layer thickness, Si particle size, and Al content accelerate the reaction rate and degree.