The possible causes of midnight acid reflux are duodenal diseases, esophageal lesions, emotional stimulation and so on. 1. Duodenal diseases: such as duodenal ulcer, duodenitis and so on. Midnight belongs to the fasting state, when the stomach has been emptied, no food to neutralize the secretion of gastric acid. When the duodenum inflammation or ulcer, gastric juice will directly stimulate the lesion, thus acid reflux, abdominal pain and other discomforts at night. 2. Esophageal lesions: the most common is gastroesophageal reflux disease (GERD), patients often have underlying gastric disease, and at night when gastric acid continues to be secreted, due to poor sleeping posture or too short a pillow, resulting in reflux of digestive juices from the stomach into the esophagus, causing acid reflux symptoms. In addition, esophageal hiatal hernia can also cause the symptoms of acid reflux at night. 3. Emotional stimulation: if the patient in the middle of the night emotional upset, depression, anger, but also easy to cause a transient increase in gastric acid secretion, resulting in acid reflux or even stomach pain, stomach bloating symptoms. Frequent occurrence of the above phenomena, need to go to the hospital as soon as possible to the gastroenterology department, under the guidance of a professional physician to clarify the cause of the disease, and active treatment.