Abstract: Monodisperse Al-4.5wt%Cu droplets with controllable particle diameters were prepared by pulsated orifice ejection method(POEM), and the particles solidified from the droplets were analyzed and characterized.The results show that the particles have the advantages of uniform particle diameter, high sphericity, same thermal history. The microstructure of particles transforms from cellular crystal to dendritic crystal with the growth of particle size.A numerical calculation model for heat transfer during particle solidification was established, and the relationship between temperature, temperature gradient, cooling rate and particle microstructure during particle falling was analyzed. Under the experimental conditions, the internal solidification structure of the 310.0 μm particle is cellular crystal, and the cooling rate is 771.71 K/s; the internal solidification structure of the 485.1 μm particle is dendrite, and the cooling rate is 382.40 K/s.