The hydriding and dehydriding properties of the tetrahydrofuran (THF) treated magnesium, along with its electronic energy states, crystalline structure and micro morphology have been investigated. The THF treated magnesium absorbs 6.3 wt% hydrogen at 723 K and 3.5 MPa. After hydrogenation, in addition to the expected hydride MgH2, a new less-stable hydride phase appears at 673 K, but not at a lower temperature. Desorption produces 5.5 wt% hydrogen at 723 K against a back-pressure of 1.3 Pa after 20 cycles of hydriding-dehydriding. The THF treatment improves the kinetics of hydrogen absorption and desorption. The THF treated Mg exhibited reasonable reaction rates with hydrogen at 623 K. XPS (X-ray Photo-electron Spectroscopy) studies show that THF treatment causes the electronic energy state of the magnesium atoms to shift, but the XRD (X-Ray Diffractometer) studies show the crystal structure remains unchanged. It is believed that the chemical state of magnesium surface is activated by THF treatment in favor of hydrogen absorption and desorption. Metallographic observation of the magnesium hydrides reveals some interesting features during hydrogenation.