The multiple cluster growth of ultra-thin films on a hexagonal substrate with fractal, dendritic and compactmorphology has been studied by computer simulation. The influence of the different diffusion processes along islandedges on the island shape has been investigated. The results show that the anisotropic coer diffusion induces thedendritic growth, and the anisotropic step diffusion can promote the anisotropic growth and cause the ramified islandsgrowing in three directions. In the case of compact growth, the island shape is mainly determined by the anisotropiccoer crossing process. The nonuniform distribution of the multiple cluster formation can be described quantitativelyby multifractal. With pattes changing from fractal to compact islands, the width and height of the bell-like orhook-like multifractal spectra increase, while the top f(α) decreases.