Abstract: In order to study the infiltration laws of ionic type rare earth and the influences of maximum particle size on infiltration laws, vertical infiltration tests on ionic rare earth were carried out by self -made testing equipment with constant water head height being 6cm, and the maximum grain sizes of samples being 0.3mm, 0.6 mm, 1.18 mm and 2.36 mm respectively. Based on the experimental results, the ionic type rare earth's saturated hydraulic conductivity and matric suction of infiltration were analyzed by the modified Green-Ampt model. The results show that the infiltration c umulative depth indicates a trend of "rapidly increasing, then slowly developing", and changing rate of wetting front, however, has a trend of "sharply decreasing, then slowly developing" with the increasing infiltration time. The relationship between wetting front changing rate and infiltration time is applied to power function, and maximum particle size of soil samples exerts a considerable influence on the parameters of power function. The infiltration rate and the reciprocal of the wetting front have a good linear correlation. Saturated hydraulic conductivity and matric suction increase with the increasing of soil sample particle size, and the relationship between both of them and the maximum particle sizes is exponential.