The i.r.spectra of Na4[UO2(CO3)3], Na[UO2(OH)3] and the surface species of uranium on HTO underthe condition of flowing natural seawater and concentrated seawater (NaCl-NaHCO3-U) were recorded, with the bands of uranyl of surface species obtained and the finding that iigands of surface species besides HTO are mainly water and OH, and there are some CO32- groups under the condition of natural seawater.Some relations between the complex properties and the j.r.spectroscopic characters for uranyl complexes were studied, and the transferred change quantity of surface complex was calculated. Structure models for surface species of adsorption are herein presented and the mechanism for uranium adsorption is deduced.