Sodium tetrahydroborate (NaBH) and dodecahydro-closo-dodecaborate (NaBH) are both important inorganic compounds presenting multiple applications. Nevertheless, multistep and complicated conditions are usually demanded for their synthesis. In order to simplify the synthesis processes, we design a novel and facile solvent-free method for synthesizing NaBH or NaBH from NaNH and BH. The product of either NaBH or NaBH is manipulable by simply adjusting the ratio of NaNH to BH. The reaction equations of synthesizing NaBH and NaBH are proposed and verified, and the reaction pathways are elucidated. The findings here supply new insight to synthesize metal dodecaborates using the strategy of equal electron body for the first time and may shed light on synthesis of small metal B-H compounds from large B-H clusters.