Abstract: Diffusivity of 3H and 90 Sr are measured in soil aerated zone on both natural condition and artificial rainfall condition The migration regularity of 3H and 90 Sr are studied in loess aerated zone at the same time. The results show that the migration velocity of 3H tracer in aerated zone is 0.03 cm/d on natural condition in loess plateau of Huabei Region, the vertical diffusivity D x is 0.52 cm 2/d; In the experiment pit, the migration of 3H is 2.27 cm/d on artificial rainfall condition(the sprinkling intensity is 5 mm/h, 3 hours each day), the vertical diffusivity D x is 7.75 cm 2/d. The 90 Sr tracer in aerated zone haven't migrated, the migration velocity is 3.7×10 -3 cm/d, the vertical diffusivity D x is 0.03 cm 2/d.