Abstract: Field results at Luancheng Agro-ecosystem Station，CAS show that the most sensitive stage to water stress for winter wheat falls on jointing ，then the following are booting and heading to flowering stages，while too much water supply during turning green to lifting will reduce winter wheat yield．The critical levels of soil water content for winter wheat are no less than 65% of field capacity for 0～50cm soil layer during jointing stage，60% for 0～80cm during booting to heading and 60% for 0～OOcm during heading to initial milky stage，50% for 0～lOOcm during milky stage，respectively．At those stages，when soil water content is below the critical level，yield will be greatly reduced．Based on the results，regulated deficit irrigation system is established for winter wheat．