The lattice dynamical, dielectric properties and thermodynamic properties of LiNH2 are investigated by first principles calculations. Based on the density functional perturbation theory within the framework of linear response theory, the phonon dispersion curves and the phonon density of phonon states throughout the Brillouin zone are obtained. The calculated frequencies of the Raman active and infrared active modes are compared with previous experimental and theoretical results, and Born effective charge tensor as well as electronic dielectric permittivity tensor is presented. We find that the Born effective charge tensor of LiNH2 has quite small anisotropy. These calculated results are in good agreement with available experimental and theoretical values. Furthermore, the thermodynamic functions are predicted using the phonon density of states.