Fundamental researches on complex hydrides are recently of great importance to develop practical hydrogen storage materials with higher gravimetric hydrogen densities than those of conventional materials. First, in this paper, we clarify the correlation between B-H atomistic vibrations in [BH4]－-anion and melting temperatures of MBH4 (M = Li, Na, and K) as indexes of hydrogen desorption temperatures. This investigation implies that partial cation substitutions using smaller sized- and/or higher valenced-cations with higher electronegativities might provide higher energy modes of Raman spectra, and then, lower hydrogen desorption temperatures. Next, as an example, LiNH2 and its partial cation substitution materials are examined. At the start of the reaction, the hydrogen desorption temperature for LiNH2 with partial cation substitution drastically decreased, with the increase in Mg concentration, to around 370K for the sample with x = 30.