Abstract The intra-molecular proton transfer of octahydrotriborate, [B H ] , is discovered by density functional theory (DFT) computational studies; such a transfer can largely impact its dehydrogenation pathways. The DFT calculation results further disclose the generation of another triborane intermediate product, B H , which is formed via inter-molecular proton transfer from [NH ] to [B H ] . Additionally, this intermediate product is unstable and can release hydrogen easily, as the corresponding energy barrier via this pathway is only 12.0 kcal mol . Such a relative energy is much lower than that of the routinely raised pathway, which mainly depends on the dihydrogen interaction between the (Formula presented.) and (Formula presented.). This new mechanism is able to explain several experimental observations involving the dehydrogenation of NH B H . Moreover, the detailed dehydrogenations of NH B H in different states are also studied, and the role of chemical environment during dehydrogenation is demonstrated. 3 8 3 9 4 3 8 4 3 8 4 3 8 − + − −1