Abstract: The hydrate of titanium dioxide is the most promising absorbent for adsorbing uranium from sea water. The state of iron (~2%) in the adsorbent has been investigated by measuring its Mossbauer effect. The Mossbauer spectrum of the original sample and calcined sample at 180℃, 340℃, 1000℃ were measured at room and liquid nitrogen temperatures. The γ-FeOOH state of iron was confirmed. Their Mossbauer spectra show a doublet, whether the samples is calcined or not. The Mossbauer parameters are isomer shift of 0.37mms-1, 0.49mms-1 and quadrapole spliting of 0.62mms-1, 0.68mms-1 at room and liquid nitrogen temperatures respectively. The sample was calcined to 1000℃ and the six finger pattern expected if Fe2O3 was formed from γ-FeOOH was not observed. The reason is: the hydrate of titanium dioxide is largely converted into TiO2 at calcination, and a few γ-FeOOH transforms into Fe2O3. The Fe3+ ion dissolves into the rutile constitution of the TiO2, forming low-adulterate state, so the six finger pattern of Fe2O3 is not observed. ,The Mossbauer parameters are isomer shift of 0.39±0.02mms-1, 0.45±0.02mms-1, quadrapole splitting of 0.70±0.02mms-1, 0.71±0.02mms-1 at room and liquid nitrogen temperature respectively. These results agree with the results of X-ray diffraction and those of differential thermal analysis.The γ-FeOOH in the adsorption of uranium from sea water may act in two ways as follows:(1) Direct adsorption It can be shown that the adsorbent produced at pH = 5-6 has higher adsorbability than at other pH. Just then the γ-FeOOH is being produced. It was proved earlier that oxyhydroxide of iron can adsorb heavy metal ions. Perhaps the γ-FeOOH has the same adsorbing effect.(2) Some kind of "catalytic" action After heating, Fe3+ ion dissolves into rutile constitution of the TiO2, therefore the γ-FeOOH probably is highly dispersed in the adsorbent. Just like some sort of low-adulterate state of iron in an insulator can change their electrical property, the adsorbent can raise its ability in adsorbing uranium in the same way.