Based on the field infiltration experiments of natural freezing and thawing'soils within the freezing and thawing periods, in this paper the freezing and thawing features of cultivated soils are analysed, the basic characteristics of reduction infiltration of freezing and thawing soils are discussed, and the reduction infiltration mechanism of freezing and thawing soils is inquired into. The results indicated that at different freezing and thawing stages, the formation, thickness, number and position of frozen layers in soils are different and the frozen layers have different control and effect on infiltrating flow, that the characteristics of reduction infiltration varies with the freezing and thawing stages, and that under freezing and thawing conditions, reduction of soil water conductivity is the basic reason for reduction of soil infiltration ability and the phase change of liquid water in soil is the origin of the reduction of soil water conductivity. The results are of theoritical value to further study on the infiltration law of field freezing and thawing soils in the districts with seasonal freezing and thawing soils and are of practical value to determine technical parameters for saving-water irrigation within the winter and spring irrigation in these districts.