The reaction of aluminum with water is of great interest to hydrogen production. However, it is very difficult to initiate the reaction owing to the oxide film covering the aluminum powder surface, especially for the reaction of micrometer-aluminum powder with water. Na2CO3 was invoked as a modifier to improve the hydrogen yield of the reaction of micrometer-aluminum with water at low temperatures. The effects of solution concentration and temperature on the hydrogen yield were studied. The results indicate that the hydrogen yield of the reaction of micrometer-aluminum powder with water without the addition of Na2CO3 is low owing to the low activity of micrometer-aluminum powder. Increasing the temperature, the hydrogen yield increases slightly. However, when Na2CO3 is added into the mixture of micrometer-aluminum powder and water, the hydrogen yield is significantly improved owing to the production of OH- of Na2CO3 hydrolysis to destroy the oxide film on the micrometer-aluminum powder surface. The hydrogen yield of micrometer-aluminum powder and water with the addition of 3 wt% Na2CO3 reaches 89.90% at 70 degrees C. There are two stages in the reaction process of micrometer-aluminum powder and water with the addition of Na2CO3: the fast reaction stage and slow reaction stage. The reaction activation energy of micrometer-aluminum powder with water increases with the increase of Na2CO3 concentration. Based on these results, the reaction mechanism is discussed.