A significant obstacle in the large-scale applications of sodium borohydride (NaBH 4 ) for hydrogen storage is its high cost. Herein, we report a new method to synthesize NaBH 4 by ball milling hydrated sodium tetraborate (Na 2 B 4 O 7 • 10H 2 O) with low-cost Al or Al 88 Si 12 , instead of Na, Mg or Ca. An effective strategy is developed to facilitate mass transfer during the reaction by introducing NaH to enable the formation of NaAlO 2 instead of dense Al 2 O 3 on Al surface, and by using Si as a milling additive to prevent agglomeration and also break up passivation layers. Another advantage of this process is that hydrogen in Na 2 B 4 O 7 • 10H 2 O serves as a hydrogen source for NaBH 4 generation. Considering the low cost of the starting materials and simplicity in operation, our studies demonstrate the potential of producing NaBH 4 in a more economical way than the commercial process.