The transition metal M (Ti, V, Mn, Co) substituting for parts of Li in the LiNH2 hydrogen storage materials have been studied by plane wave pseudopotential methods based on the first principles and the density functional theory. The crystal and electronic structure, binding energy, and H vacancy formation energy for Li(M)NH2/M(=Ti, V, Mn, Co) were calculated. Results show that the stability of the Li(M)NH2 and the bond strength between N and H atoms are reduced when the Li atoms of LiNH2 are partially replaced by the Ti, V, Mn, or Co atoms. The best effect is got by Ti doping. The calculated vacancy formation energy of Li(M)NH2 is 1.365, 0.829, 0.486, and –0.079 eV for M=Ti, V, Mn and Co, respectively. It is found that the decreased dissociation energy of H is obtained by Ti, V, Mn, Co substitution to Li of LiNH2, showing the improvements of the dehydrogenation ability for Li(M)NH2. The effect of Ti is better as a catalyst than that of V, Mn, and Co.