There are many factors that may cause patients to have fever and spit up yellow sputum, and they may be caused by the following factors: 1. Pneumonia caused by pathogenic bacteria such as Streptococcus pneumoniae in the lungs, usually patients will have high fever, body temperature up to 38.5℃ or more, and cough up more sputum and even have symptoms such as difficulty in breathing and chest pain. 2. If the patient has fever, spitting yellow sputum with less volume and blood in the sputum, it may also be caused by infectious diseases such as tuberculosis. 4. Chinese medicine generally considers fever and spitting yellow sputum to be symptoms of cough and fever caused by wind-heat.