A new method dispersed Si nanoparticles in the process of pulsed laser ablation (PLA) was proposed in this paper. A single crystalline Si target with high resistivity of 3000 Ω·cm was ablated by a XeCl excimer laser (wavelength: 308 nm, laser fluence: 3 J/cm2) in high-pure Ar gas at the ambient pressure of 10 Pa, and the Si nanoparticles were systemically deposited on glass or single crystalline Si substrates located at a distance of 2.0 cm under the plume. The Raman spectra indicate that Si nanoparticles were obtained in the samples at different horizontal distances, 0.5～2.8 cm, from Si target. The scanning electron microscopy (SEM) images show that the average size of Si nanoparticles gradually decreased with increasing the distance from the target. The experimental results were explained by ablation dynamics. Because Si nanoparticles with different masses gained the different horizontal velocity, Si nanoparticles were dispersed according to their sizes under gravitation.