The reactor is very critical to intensify the reaction rate controlled by mass transfer. Solid magnesium hydride (MgH2) shows great advantages in hydrogen storage; however, poor liquid–solid hydrolysis kinetics limit its application. Various chemical reactors were explored and are used to improve the hydrolysis efficiency. Results show that the mixing style could affect the surface coating behavior. Specifically, the higher temperature and mixing strength could promote the MgH2 hydrolysis. Furthermore, induced crystallization could effectively relieve coating and strengthen the hydrolysis, especially at the high mixing level. The result indicated that the mass transfer distance between crystal seed and formed MgH2 particles played an important role in MgH2 hydrolysis.