Crop water requirement is important to irrigation requirement planning and water resources planning. Understanding historical changes and future trends is critical to predicting future crop water use trends and making rational decisions. Using the Penman- Monteith model recommended by the FAO, the water requirement of spring maize across the whole plantation in northwestern Liaoning was calculated. The net water requirement of spring maize at different growth stages was obtained by soil moisture density function under full irrigation conditions. We found that potential evapotranspiration and spatial and temporal variation in water demand indicates that spring maize increased and decreased over the last 50 years. In the past 50 years, the water demand of spring maize in northwestern Liaoning has not decreased over time. The spatial distribution has gradually increased from southeast to northwest. From net irrigation water demand, the average annual net irrigation water requirement of spring maize in northwestern Liaoning was 402.44 mm, and average annual irrigation requirement index was 0.67. From the perspective of net irrigation water demand under future climate change scenarios, domestic or regional resources (A_2) scenarios and regional sustainable development (B_2) scenarios, the 30 a growth rate decreased in turn. This study provides a basis for agricultural water use and reasonable irrigation of spring maize planting in the northern Liaoning. It is of great strategic significance to the increasingly prominent contradiction between supply and demand of water in this region.