Abstract: With the effect on soil wetting pattern, the dripper discharge has influence on crop roots development. In the design of drip irrigation system, the dripper discharge should be reasonably determined according to the relationships between dripper discharge and soil wetting pattern. Based on the equivalent cylindrical pattern of soil wetting front, the model of dripper discharge was developed mathematically, and the change of each factor with the dripper discharge was analyzed to determine the main influential factors of dripper discharge design for drip irrigation system. The experimental soils were clay soil, loam clay and sandy soil; while the experimental dripper discharges were 1, 2, 3 and 4 L/h, respectively. The results indicate that dripper discharge has more influence on the horizontal distance of soil wetting front than that on the vertical one. Soil saturated pond could control the horizontal distance of soil wetting front. In the design of the drip irrigation system, the dripper discharge should be determined on the designed soil wetting proportion (or wetting diameter), except for the soil infiltration characteristics.