Abstract: Due to the increase in cropping area and the proportion of water-intensive crops, the contradiction between the water supply and demand of water resources for grain production has been exacerbated in the three provinces of Northeast China (NEC). Green water, as the main water resource for grain production in NEC, plays a pivotal role in alleviating the water-grain contradiction. Here, we quantified the green water deficit (GWD) of major grain crops (rice, corn, and soybean) in NEC at multiple spatial and temporal scales, based on the meteorological data and crop data for the period 2001-2020 using the Penman-Monteith equation. The results show that the GWD of rice ranges from 50 to 125 mm in wet years and exceeds 230 mm in dry years, and it reaches to almost 400 mm in dry years in Songnen Plain and Sanjiang Plain, which are the highest GWD regions for rice. Green water supply for corn is sufficient in wet years but insufficient in dry years, with an average deficit of 70 mm. And spatially, the GWD is smaller in the mountainous regions while larger in the plains, with a decreasing trend in the plains. The green water supply for soybean is relatively adequate, and only the southern Songnen Plain and the southwestern Liaohe Plain may have a deficit of about 100 mm in dry years. We also analyzed the GWD at key growth stages of each crop to characterize the seasonal GWD. In general, rice, corn, and soybean have GWD in the critical water demand periods in 80%, 85%, and 50% of the years, respectively, with GWD ranging from 20 to 60 mm annually. It is worth noting that the critical water demand for corn is also its most severe GWD period, indicating the adverse impact on corn yield will possibly be higher as it is mainly a rain-fed crop in NEC. The most severe GWD period for rice is tillage stage, with an average annual deficit of about 70 mm, but this deficit can be compensated by blue water irrigation. The maximum seasonal GWD of soybean occurs during the maturity stage, which is lower sensitive to GWD. Therefore, seasonal GWD will have the greatest effect on corn yield. The interannual, seasonal, and regional differences in GWD are significant, and the total amount of GWD (TGWD) will further increase in consideration of the planting scale. For example, the average TGWD in dry years is 20 billion m³ and is 6.5 billion m³ in wet years, respectively. The Songnen Plain has the largest TGWD, ranging from 1.5 to 2.0 billion m³, followed by the Sanjiang Plain, where the TGWD is nearly 0.5 billion m³. Overall, the contradiction between water supply and demand is lower in the mountainous regions and higher in the plains, where crops are widely distributed. Therefore, the contradiction between water supply and demand in plains will put continuous pressure on water resources in NEC. The results of this study can promote the understanding of water-crop relationship and provide scientific information for agricultural water management in NEC.