Chest pain when lying down may be related to costochondritis, reflux esophagitis, muscle strain and so on. 1. Costochondritis: mostly caused by non-infectious factors, chest pain and pressure pain, caused by infectious factors may also appear local skin redness, swelling, heat and pain. The pain will be aggravated during strenuous activities or coughing, and the chest pain may also be felt when lying down. 2. Reflux esophagitis: When lying down, the pressure in the area where the esophagus meets the stomach decreases, which is more likely to cause gastric acid to reflux into the esophagus, resulting in burning, pain and discomfort at the back of the sternum, which may be accompanied by acid reflux, nausea and loss of appetite. 3. Muscle strain: If there is overwork or strenuous exercise recently, the chest muscles are strained, and the symptom of chest pain after lying down can also appear. Lying chest pain symptoms, if the symptoms continue to be unrelieved or gradually aggravated, you should go to the hospital in time to find out the cause of treatment under the guidance of the doctor.