The common causes of dry mouth are as follows: First, diabetes, if dry mouth is combined with symptoms such as easy hunger, excessive urination and lethargy, attention should be paid to exclude diabetes. If necessary, we can go to the hospital and perform blood glucose and glucose tolerance tests to further clarify the diagnosis; Second, dry mouth, if dry mouth is combined with dry eyes, saliva and tear secretion significantly reduced, we should pay attention to except dryness, and we should go to the rheumatology and immunology clinic to check anti-nuclear antibody and immunoglobulin tests. If necessary, oral mucosa biopsy should be performed to clarify the diagnosis; thirdly, open-mouth breathing, open-mouth breathing can cause the occurrence of dry mouth symptoms, at this time, if the patient changes the way of breathing, the symptoms of dry mouth can be significantly relieved.