Ultrasensitive C-reactive protein is a blood test whose results can be used for guidance in infectious diseases and cardiovascular diseases. Elevated ultrasensitive C-reactive protein often indicates inflammation in the patient’s body, such as bacterial infection, viral infection, etc. It is also seen in myocardial infarction, malignant tumor, surgical trauma, trauma-induced tissue damage, etc. Elevated ultrasensitive C-reactive protein cannot be used directly for disease diagnosis, but it can be used as a reference for clinical diagnosis and treatment of diseases. If a patient has fever with cough and sputum, combined with elevated ultrasensitive C-reactive protein, it is considered to be caused by respiratory tract infection. If the patient has persistent chest pain and profuse sweating, elevated ultrasensitive C-reactive protein, combined with myocardial enzymes and electrocardiogram changes, it is necessary to consider the possibility of acute myocardial infarction.