Particle-reinforced metal matrix composites via the Osprey spray casting process were fabricated by injecting second phase particles of Al₂O₃(＜40㎛) and W(6㎛) into the spray of Cu droplets, and the thermal behaviors of the composite droplets during flight were considered theoretically on the basis of mixing modes between the Cu droplets and the reinforced particulates injected. It was found that the W-injected spray is comprised of particle-embedded droplets, and the Al₂O₃-injected spray comprises particle-attached droplets. From the predicted results of the thermal behaviors of the composite droplets and preforms produced, it is concluded that the thermal behaviors of the composite droplets during flight, and during the subsequent deposition are strongly influenced by its mixing modes between the reinforced particulates and Cu droplets during flight.