The invention provides an application of speckled prevotella in treatment or prevention of rheumatoid arthritis or related diseases thereof, and also provides speckled prevotella containing pharmaceutical compositions, medicaments, foods and feeds. By providing speckled prevotella for animals, an anti-inflammatory effect can be effectively played, the symptoms such as redness and swelling of joints are effectively improved, the symptoms of arthritis are obviously relieved, and therefore, the speckled prevotella can be effectively used for treating or preventing rheumatoid arthritis or related diseases thereof.
