Postnasal cavity to the throat always have phlegm, may be chronic rhinitis caused by adverse symptoms, may also be suffering from chronic sinusitis, nasopharyngitis and other diseases. 1. Chronic rhinitis: chronic rhinitis can cause the postnasal cavity to the throat always have phlegm, mainly due to inflammation stimulation of nasal secretions increase, breathing or coughing into the nasopharynx caused by the discomfort. 2. Chronic sinusitis: chronic sinusitis will lead to nasal cavity pus secretion, flow to the nasopharynx will also cause such discomfort, suffering from such diseases will also appear headache, nasal congestion, facial distension and other adverse symptoms, some patients will have a dysfunctional sense of smell. 3. Nasopharyngitis: the post-nasal cavity connected to the throat always have phlegm, may also be the nasopharynx itself there is inflammation caused by the discomfort, the posterior wall of the nasopharynx will be attached to a large number of secretions, coughing or inhalation will make the secretion will be gathered, a large amount of phlegm, may be accompanied by headache, frequent nasal retraction and other manifestations. There may be other reasons for this condition, so it is necessary to go to the hospital in time for relevant examinations, and actively cooperate with the doctor after diagnosing the cause of the disease to avoid aggravation of the condition.