Legionnaires' disease (legionella pneumonia) is a systemic disease caused by Legionella bacteria with pneumonia as the main manifestation. There are 40 species of Legionella, most of which are clinical isolates of Legionella pneumophila, followed by Legionella micdadei, and others are rare. It is a Gram-negative bacillus, but the color is lighter. It is a strict aerobic bacterium, and has special nutritional requirements during the initial isolation and culture. It requires the use of selective special culture media containing antibiotics, cysteine, and iron, such as activated charcoal yeast agar (CYE) and BCYE-α culture media. The key to ensuring the success of bacterial culture and isolation is to adjust the accurate pH value of the culture medium and a certain concentration of CO2 environment (2.5% to 5%) and the culture time (at least 5 days). The detection rate of this bacterium in clinical laboratories is very low, and most of the diagnosis of this disease is based on serum antibody determination.