The nonlinear propagation characteristics of intense laser with circular aperture diffraction in Kerr medium are stuied by experiments. We experimentally observe the formation of small-scale filaments, the evolution of single filament and the interaction between filaments. Results show that modulation growths take place at particular spatial positions and lead beam breakup into multi-filamentation during nonlinear propagation. The single filament intensity is not growing indefinitely, but to release the excess energy by the cone emitting after reaches a certain value. At the same time, new filaments form owing to the interaction between the background energy and the released energy. The filaments in close proximity through the interference interaction, make new filaments form in their neighborhood.