A common cause of spitting green phlegm in the throat sometimes is Pseudomonas aeruginosa infection. There are many diseases in which Pseudomonas aeruginosa infection exists, commonly acute upper respiratory tract infections, bronchitis, pneumonia, tuberculosis, and long-term use of ventilators. Spitting green sputum is a characteristic sign of infection, as the patient is infected by Pseudomonas aeruginosa, resulting in increased secretion from the mucous membranes of the respiratory tract, while the inflammatory secretion contains a large number of Pseudomonas aeruginosa resulting in sputum that is green in color. Pseudomonas aeruginosa is a common opportunistic pathogen and an important cause of hospital-acquired infections. People with this symptom should go to the hospital in time for diagnosis and treatment, as untreated cases may evolve into bacteremia, sepsis and other dangerous diseases, and should not use medication on their own to avoid danger.