Nitrogen plays an important role in plant growth and development. Melatonin (Mel) is involved in many physiological and biochemical reactions in plants, which can enhance the resistance of plants to abiotic stress. However, the mechanism of exogenous Mel in maize seedlings under low nitrogen stress is still unknown. This experiment adopts the method of sand culture, Zhengdan 958 was used as the experimental variety, and three nitrogen levels (5mmolL