The elastic and optical properties of face-centered cubic IVB group transition metal nitrides such as TiN, ZrN, and HfN are calculated using the plane wave pseudopotential method based on first-principle density function theory. Electronic property is a combination of covalent, ionic, and metallic property. And band structures of these compounds show metallicities in the ground state. The obvious numerical differences between E[100] and E[111] indicate elastic anisotropy. The phenomena result in lattice distortions and microcracks in these metal nitride films. With red shift of pseudogap, the metallic properties of TiN, ZrN, and HfN are improved in turn. And the elastic and optical properties change with metallic properties improving:brittleness reduces, the degree of anisotropy increases, the critical energy between intraband and interband transitions increases, and the solar-optical selectivity decreases. So reducing the number of conduction electrons to strengthen covalency is an effective method to improve elastic isotropy and optical selectivity.