Abstract: The transport behavior of U(Ⅵ) in the presence of soil colloids was investigated by column experiments using quartz sand as the porous media, and batch technique was further applied to explore the mechanism of U(Ⅵ) transport in the presence of soil colloids. The results show that when the initial mass concentration of U(Ⅵ) increases from 1.0 mg/L to 5.0 mg/L, the transport rate of U(Ⅵ) significantly increases, and the required leachate volume increases from 250 PVs(pore volume) to 400 PVs, reaching the elution equilibrium. Compared with U(Ⅵ), the soil colloids transport much faster in the quartz column, mainly owing to the weak interaction between the soil colloids and the quartz sand. In the presence of soil colloids, the transport rate of U(Ⅵ) is remarkably improved, while the breakthrough curve of soil colloids do not change obviously, which indicates that the transport behavior of U(Ⅵ) in the ternary system of colloid-U(Ⅵ)-quartz is mainly controlled by soil colloids. In the binary system of U(Ⅵ)-quartz, the sorption of U(Ⅵ) on quartz is maximized at pH≈6.0, while in the ternary system of colloid-U(Ⅵ)-quartz almost all U(Ⅵ) is absorbed on the soil colloids, and the contribution of quartz can be negligible. It is noted that about 20% U(Ⅵ)(initial mass concentration is 5.0 mg/L) is adsorbed on soil colloids, which only accounts for 0.04% of the studied soil. The strong interaction between soil colloids and U(Ⅵ) suggests that soil colloids have a crucial impact on U(Ⅵ) adsorption, transport and diffusion in the environment.