Water stress affects maize leaves' photosynthesis and water use efficiency. The study used water stress and rewatering experiments on maize in different growth stages. Results showed that water stress decreased photosynthesis rate, transpiration rate, and stomatal conductance. Maize adapted to drought by reducing these values, improving water use efficiency. Moderate water stress actually increased water use efficiency, helping maize resist drought. However, prolonged and severe water stress inhibited photosynthesis, especially from jointing to silk stages.