The invention provides an application of haemophilus parainfluenzae in treating or preventing rheumatoid arthritis or related diseases thereof, and also provides a pharmaceutical composition, a medicament, a food and a feed containing the haemophilus parainfluenzae. By providing the haemophilus parainfluenzae for animals, an anti-inflammatory effect can be effectively brought into play, the symptoms of rubefaction and swelling of joints can be effectively improved, and the symptoms of arthritis can be obviously relieved, so that the haemophilus parainfluenzae can be effectively used for treating or preventing the rheumatoid arthritis or the related diseases thereof.
