The ground states of plutonium dihydride under electric field ranging from -0.005 to 0.005 a.u. have been optimized using density functional theory DFT/B3LYP with SDD for Pu and 6-311++G** for H. The excitation energies and oscillator strengths have been calculated under the same electric field employing the time-dependent DFT method. The results show that the electronic state, total energy,molecular geometry, dipole moment and excitation energy are strongly dependent on the applied field strength. As the electric field changes from -0.005 to 0.005 a.u., the bond length of Pu-H increases whereas the bond angle of H-Pu-H decreases because of the charge transfer induced by the applied electric field. The dipole moment of the ground state increases linearly with the applied field strength. The total energy of the ground state decreases linearly with the applied field strength. The dependence of the calculated excitation energies on the applied electric field strength fits well to the relationship proposed by Grozema. The excitation energies of the first five excited states of plutonium dihydride decrease as the applied electric field increases because the energy gap between the HOMO and LUMO become narrower with the field, which shows that the molecule is apt to be excited under electric field and hence can be easily dissociated.