The strong solid-acid of sulfated zirconia nanocrystals is capable of catalyzing the isomerization of n-butane to isobutane at room temperature. Oxygen atoms at the nanocrystal surface directly affect the rates of catalytic reaction. Electron energy loss spectroscopy results show the difference in the oxygen K-edges of the sulfated and nonsulfated zirconia, especially in the post-edge peaks. It is proposed that the ratio between the height of post-edge peak (h) and the height of K-edge peak (H) of oxygen may be used as an indicator of the acidity and reactivity of the sulfated zirconia.