Irreversibility negatively impacts the application of NaBH4 hydrolysis for hydrogen generation. Byproduct regeneration is key to solving this issue. In this work, the direct byproduct of aqueous NaBH4 hydrolysis, NaBO2 center dot 4H(2)O, is reacted with Mg2Si to regenerate NaBH4 via ball milling at room temperature under an argon atmosphere. In this process, the H- in NaBH4 is exclusively from the H+ in NaBO2 center dot 4H(2)O. The regenerated NaBH4, with a maximum yield of 74%, has the same physicochemical properties as a commercial sample. We also demonstrate that Mg2Si reacts with NaBO2 center dot 4H(2)O to generate NaBO2 center dot 4H(2)O, followed by a direct reaction between the residual Mg2Si and NaBO2 center dot 4H(2)O to produce NaBH4. The energy efficiency of this method is approximately 40%.