Crop water source is an important aspect in the study on water cycling in SPAC (Soil Plant Atmosphere Continuum) and water-saving agriculture. Traditional approaches are not adequate to determine contributions of different water sources to the crop. Based on the winter wheat field experiment in Fengqiu, using the stable hydrogen and oxygen isotope techniques, a new model coupling a linear mixing model with δD- δ¹⁸O curves was established and used to calculate contributions of different water sources to the winter wheat at various growth stages in the Huang-Huai-Hai Plain of China. Results show that contributions of the sources to winter wheat varied with the growth stage. Soil water in the top soil layer (0～20 cm) was the main water source to winter wheat at the tillering, regreening, and jointing stages; At the booting stage, the crop got its water mainly from the soil at 80 cm in depth; At the flowering stage, it turned to the soil at 80 and 180 cm in depth for water supply; To wheat at the milk stage, soil water at 40 and 80 cm in depth contributed 47.5% and 39.5%, respectively, of the total the crop needed; And at the booting and flowering stages, the crop took 9.0% and 16.4%, respectively, of the water it used up from groundwater.