Most of the yellow pus nasal discharge suggests sinusitis, which may be caused by the following factors: first, bacterial infection, mostly secondary to upper respiratory tract infection, clinically Streptococcus pneumoniae and Staphylococcus aureus are more common, anaerobic bacteria are also present, many bacteria mixed together are more common, because of the bacterial infection, so it is easy to have yellow pus nasal discharge. Secondly, some patients have dental infections, such as odontogenic maxillary sinusitis, which also manifests as yellow pus nasal discharge. The third kind is more common in children, such as children with adenoid hypertrophy blocking the posterior nostrils, resulting in poor nasal drainage and bacterial infection in the nasal cavity, thus manifesting as yellow pus nasal discharge. Fourthly, some patients have foreign bodies in the nasal cavity, which also occur in children, and the foreign bodies are stored in the nasal cavity for a long time, resulting in local infection in the nasal cavity and thus manifesting as yellow pus nasal discharge.