Organic dyes such as vanadium (IV) oxo(phthalocyaninato) (VOPc) nanoparticles have been fabricated by pulse laser ablation in aqueous solution. Under the condition of the same total incident light energy, the average diameter of VOPc nanoparticles, observed by an atomic force microscopy (AFM), increases with the pulse laser energy density. The ultraviolet-visible light (UV-Vis) absorption spectrum of VOPc nanoparticles colloid solution indicates that there is no more contribution for producing nanoparticles by so longer laser irradiation time. The nanoparticles reaggregation directly influences the preparation efficiency and the size of the produced nanoparticles, and finally it will achieve dynamic equilibrium with the process of producing nanoparticles. In aqueous solution the hydrophobic force is the main reason for the nanoparticles reaggregation.