The yellow water coming out of the nose when the head is lowered has the following main clinical causes: 1) acute sinusitis attack. 2) manifestation caused by rupture of sinus cysts. 3) symptoms caused by skull base fracture and cerebrospinal fluid nasal leakage. Patients need to go to the hospital for a detailed examination of the electronic rhinoscopy, sinus CT and head CT, and nasal secretion laboratory tests to confirm the diagnosis of lesions. In terms of treatment, if it is an acute inflammatory infection, symptomatic anti-inflammatory treatment is needed, and the use of antibiotics will gradually cure it. In case of repeated rupture of sinus cysts, surgical removal of sinus cysts can be cured. In the case of cerebrospinal fluid leakage, the first step is to stay in bed and rest, which can be cured in a month or so. If it does not heal, local skull base surgery is needed to repair the leak.