Colloid transport in porous media is controlled,to a large extent,by surface properties of the colloid perse and physical and chemical factors,like ionic strength,pore water velocity,etc. An outflow experiment using saturated quartz column was conducted and designed to have three level of ionic-strength(i.e. 0.001 5,0.01 and 0.03 mol L^-1)and two pore water velocities(i.e. 21 and 5 cm h^-1)to analyze deposition and transport process of Kaolinite and SiO₂. Results show that deposition processes of Kaolinite and SiO₂ were distinctly enhanced with increasing ionic strength,while higher pore water velocity tended to facilitate movement of Kaolinite and SiO₂,thus covering a much longer transport distance.Further analysis indicates that ionic strength and pore water velocity had a more significant impact on transport of Kaolinite(≥500 nm in particle size)than of SiO₂ (190 nm in diameter).The findings may further understanding of the mechanism of colloid promoting transport of pollutants,and are of some guiding significance to overall objective assessment of pollution risks of the underground environment.