Early warning for agricultural water security can be divided into water quantity and water quality early warning. Based on agricultural water supply and water requirement analyses, and trends in water supply and water requirement, agricultural water security in the northeast region of China is forecasted. According to the ratio of agricultural water supply and requirement, trends in agricultural water are ranked in different classes. In the current water supply and Wetter-consuming mode, the northeast region water resource is scarce. The water resource situation is better in the current water supply and water-saving mode or potential water supply and water-consuming mode compared with the current water supply and water consuming mode; however water supply is inadequate for development. Before 2030，agricultural water could be secured by the potential water supply and water-saving mode，but currently up to 2030 in the no warning situation, there is a 1.57*10¹⁰m³ water shortage. To address the problem of the agricultural water, suggestions are presented to ensure agricultural water security.