Abstract: The first-principles calculation was carried out for the novel Ge₃N₄ compounds through the plane-wave pseudo-potential method. The results showed that the tetragonal, monoclinic and orthorhombic structures can retain their stabilities at 0 GPa. o-Ge₃N₄ has the highest tensile resistance and hardness among the three phases. The phonon dispersion, dielectric function, energy loss function and optical absorption are successfully obtained. Ge₃N₄ have weak absorptions in the visible light region, and the UV absorption characters are strong. The peak of the imaginary dielectric function is mainly contributed by the electron transitions from the N-2p band to the Ge-4s and 4p bands. The phonon dispersion curves reflect the characters between hybridization of N and Ge. Besides, the static dielectric constant and plasma frequency of t-Ge₃N₄, m-Ge₃N₄ and o-Ge₃N₄ are also obtained.