Abstract: The relation between infiltration time and wetting front depth is solved by the Darcy's law and the conservation of mass which is equal to the time derivative of cumulative infiltration, but both cumulative infiltration of completely saturated wet area and the infiltration rate derived from Green-Ampt model which ignores air resistance effect limit the calculation accuracy between infiltration time and wetting front depth. In order to solve this problem, the model is modified through stratified assumption and adding air resistance. The corrected results are used to solve the relationship between the infiltration time and the wetting front depth. The results show that at the same infiltration depth, the calculated infiltration time considering gas resistance term in the stratified hypothesis model agrees with the measured value. And the deviation degree is very low, and there is only a very small fluctuation. The test results play an important role in confirming the infiltration time of stable infiltration of sand layers.