The phase transformation and hydration of the NaBr and mixed NaBr and Mg(NO<sub>3</sub>)<sub>2</sub>･6H<sub>2</sub>O particle were investigated in a electrodynamic balance (EDB), in which a levitated single particle of diameter about 10-50μm is in dynamic equilibrium with water vapor under controlled conditions. Raman spectroscopy was used to observe the phase transitions in an electrodynamically levitated microparticle. For the deliquescence-mode experiments of a NaBr particle, two steps with a rapid increase of particle mass were corresponded to two phase transitions from NaBr anhydrate particle to the dihydrate solid particle and from the dihydrate to the aqueous solution droplet respectively. In crystallization mode experiments, the NaBr solution droplet recrystallized as the stable anhydrate. In the case of the mixed particle of NaBr and Mg(NO<sub>3</sub>)<sub>2</sub>･6H<sub>2</sub>O, ion exchange reaction took place during the deliquescence-crystallization experiment and the mixed particle of NaNO<sub>3</sub> and MgBr<sub>2</sub>･6H<sub>2</sub>O was fully formed upon efflorescence.