Two-year-old baby crying in the middle of the night may be caused by environmental factors, digestive diseases, rickets, calcium deficiency and other reasons. 1. Environmental factors: when the baby’s sleep environment is noisy or the light is strong, it is likely to lead to crying in the middle of the night. Parents can improve the baby’s sleeping environment to ensure the quality of the baby’s sleep. 2. Digestive diseases: it may be indigestion, gastroenteritis and other digestive diseases that cause babies to cry in the middle of the night, and there may be abdominal pain, diarrhea and other symptoms. 3. Rickets: mainly caused by vitamin D deficiency, babies may have night terrors, irritability, excessive sweating and other symptoms. 4. Calcium deficiency: Calcium deficiency can lead to nerve excitation, which causes babies to cry in the middle of the night. If the two-year-old baby crying in the middle of the night is pathologic, it is recommended to seek medical attention as soon as possible so as not to delay the treatment of the disease.