The hydrolysis reaction of LiH powder has been investigated in order to determine the products, rates and mechanisms of this reaction and the influence of the experimental parameters. Raman spectroscopy, X-ray diffraction and gravimetric analysis were used. It was shown that the product of hydrolysis was the hydroxide of lithium (LiOH) for low partial pressure of water (≈50Pa) and LiOH·H 2 O for a higher partial pressure of water (>2000Pa). Moreover, data obtained using gravimetric analysis inside a glove box containing a controlled partial pressure of water (500ppmv/50Pa at 25°C) were used to determine the rate of the reaction versus particle size. The experimental results were consistent with the shrinking core model showing that initially, the conversion rate is controlled by the chemical reaction.