Abstract: Tracer migration experiment of stable element, strontium, is conducted in both unsaturated and saturated columns with undisturbed loess. It is found from the experiment that retardation coefficient, Rd, of Sr can be joined up very well. It can be seen that retardation cefficient, Rd, of Sr in loess is not constant and increases with water flow velocity either in unsaturated columns or in saturated columns, as well as migration velocity of Sr at unit sprinkling rate decreases with sprinkling rate according to positions of either peaks or mass centers. It is shown that to use equilibrium adsorption model is not proper for describing migration of Sr in loess.