The vertical distribution of salt in the soil profile in the salt-affected areas of the Huang-Huai-Hai Plain is characterized by intensive salt accumulation at the soil surface and its rapid changes with seasons. To regulate salt distribution in the soil profile, an additional fraction of irrigation water, other than leaching specially, would let crops stand to survice. The additional amount of water is called Irrigation Leaching Requirement (ILR). By soil column experiments and numerical procedure, a method to ascertain the minimum amount of ILR is discussed, Results of ILR under different salt conditions are given. Based on salt tolerance of crop, ILR changed from 191 to 1350 m³/ha at seedling stage, and from 690 to 3950 m³/ha in growing period. The paper provides an approach to reclamating salt-affected soil and making efficient use of water resources.