Zirconium singlelayer films were prepared by ion beam sputtering method. By using a novel designed substrate holder in preplanting seeds method, the growth process of the nodular defects in thin films was studied. With the help of high resolution optical microscopy and electron scanning microcopy, the phenomenon that the nodules nucleation exhibits fractal characters in their initial growth period was observed. By using the molecular dynamics theory and diffusion limited aggregation model of film growth, the fractal phenomenon of the nodule nucleation was well explained.