Abstract: In order to study the effects of particle migration and ammonia ion adsorption on the permeability of coarse grained soil, the permeability test of three kinds of granite weathered coarse grained soil was carried out by a penetration apparatus. The variation law of permeability coefficient of these soil samples in the distilled water and the ammonium sulfate solution were studied. The results show that the influence of particle migration on the permeability of the soil samples decreases with the increase of fine particles in the soil, and the effect of ammonia nitrogen adsorption on the permeability of the soil sample is more obvious in the ammonia nitrogen solution environment. With the extension of the infiltration time, the permeability coefficient in different solution environments tends to be consistent, showing that the migration of fine particles have a stronger effect than nitrogen ion adsorption on the sample soil permeability. However, the ion adsorption has a certain delay effect on the reduction of permeability coefficient. On the basis of this, the evolution mechanism of the permeability coefficient of the soil samples in permeation process was discussed. The results show that the migration of particles caused by the pore blockage of the soil samples, and the changes of the thickness of the hydration film on the surface of the particles caused by the adsorption of ammonia nitrogen ions are the main reasons for the changes of the permeability of the soil samples.