Abstract: Changing laser fluence, Si nano-crystal films were prepared by the pulsed laser ablation in direct current electric field that paralleled to target surface in Ar gas of 10 Pa at room temperature. The substrates were fixed on the position with different angles to plume axis. The morphology and composition of samples were characterized by scanning electron microscopy and Raman scattering spectrums. The results indicated that the average size and the area density of nanoparticles increase with the addition of laser fluence at the same angle. The average size and the area density of nanoparticles at direction of plume axis are the biggest when the laser fluence keeps invariable, furthermore, the values of them near grounded board are bigger than those near the positive board symmetrical. The results were analyzed on the base of diagnosis of changes of silicon ions density through Langmuir probe and dynamics of nucleation and growth process of nanoparticles in the nucleation region.