Abstract: Infiltration rules of leaching solution in the process of ion-adsorption rare earth in-situ leaching play an important role in high efficiency mining and utilization of rare earth resources. One-dimensional horizontal infiltration experiment of ion-adsorption rare earth was carried out based on the self-made test device with 3% ammonium sulfate solution as the infiltration solution. In this experiment, the rules of cumulative infiltration length, wetting front velocity and infiltration rate of 4 different partical sizes rare earth were studied. The results show that the cumulative infiltration length indicates a trend of "rapidly increasing, then slowly developing"; the wetting front velocity and infiltration rate show the trend of "reaching maximum and sharply decreasing, then tend to be developing stably"; the relationship between wetting front velocity and infiltration time is a power function v=λ·t^-0.5; the saturated permeability coefficient of soil increases with the increase of the maximum particle size, and the value of which is 0.001 3~0.002 5 cm/min. The results contribute to the scientific realization of ion-adsorption rare earth in-situ leaching.