Stability of sodium borohydride solution during storage was studied. In order to enhance the NaBH4 stability, NaOH and KOH were added to the NaBH4 solution. The effect of concentration of the borohydride and alkaline solution, temperature and materials of storage vessels on the rate of borohydride hydrolysis was investigated. The rate of hydrogen evolution decreased as the concentration of alkaline increased due to increase of NaBH4 stability in the solution. The stability of NaBH4 solution decreased when the borohydride concentration raised from 10 to 15 wt% and then increased when the NaBH4 concentration increased above 15 wt% due to increase in the pH of the concentrated solution. The activity coefficient of hydrolysis of NaBH4 solution(NaOH 3.0 wt%, NaBH4 25 wt%) was 115.1 kJ/mol and this value was 1.5~4.0 times higher than that of hydrolysis of NaBH4 solution with catalyst. The borohydride solutions in glass and stainless-steel vessel were more stable than the solution in plastic(PE) vessel.