X-ray diffraction and infrared spectroscopy were used to study the mechanism of adsorption of uranyl tricarbonate ions by zinc hydroxide carbonate.The conclusions are as follows: (1) the adsorption of sodium uranyl tricarbonate by zinc hydroxide carbonate is a chemical process with the formation of a new compound,as the X-ray diffration pattern of the product is different from either that of zinc hydroxide carbonate or that of sodium uranyl tricarbonate.The new compound diffracts Cu-K_α radiation at 2θ=18.2°,22.43° and 31.9°,and the most intensive diffraction peak is at 2θ=22.43°;(2) the adsorbability increases with the relative concentration of -OH in zinc hydroxide carbonate; (3) after the adsorption of [UO₂ (CO₃)₃]⁴-by zinc hydroxide carbonate,the concentration of -OH in the adsorbent decreases.