The effect of irrigation water quality on unsaturated hydraulic conductivity (HC) of undisturbed soil in field was studied. Results show that within the operating soil suction range (0-1.6 KPa) of disc permeameters. the higher the electric conductivity (EC) of irrigation water, the higher the soil HC became. The soil HC doubled when EC increased from 0.1 to 6.0 ds m-1. High sodium-adsorption ratio (SAR) of irrigation water would have an unfavorable effect on soil HC. Soil HC decreased with the increasing of SAR, especially in the case of higher soil suction. An interaction existed between the effects of EC and SAR of irrigation water on soil HC. The HC of unsaturated soil dependent upon the macropores in surface soil decreased by one order of magnitude with 1 KPa increase of soil suction. In the study on the effect of very low soluble salt concentration (EC =0.1 ds m-1 of irrigation water on soil HC, soil HC was found to be lowered by 30% as a consequence of blocking up of some continuous pores by the d The effect of irrigation water quality on unsaturated hydraulic conductivity (HC) of undisturbed soil in field was studied. Results show that within the operating soil suction range (0-1.6 KPa) of disc permeameters. The higher the electric conductivity (EC) of irrigation Water, the higher the soil HC became. The soil HC doubled when EC increased from 0.1 to 6.0 ds m-1. High sodium-adsorption ratio (SAR) of irrigation water would have an unfavorable effect on soil HC. Soil HC decreased with the increasing of SAR, especially in the case of higher soil suction. An interaction existed between the effects of EC and SAR of irrigation water on soil HC. The HC of unsaturated soil dependent upon the macropores in surface soil decreased by one order of magnitude with 1 In the study on the effect of very low soluble salt concentration (EC = 0.1 ds m-1 of irrigation water on soil HC, soil HC was found to be lowered by 30% as a consequence of blocking up of some continu ous pores by the d