Abstract: Comorbidity of autoimmune diseases is a very important issue but easily ignored in the clinical practice. The treatment of comorbidity of autoimmune diseases needs cooperation of multiple disciplines, which is totally different from traditional clinical disciplines division and treatment mode. Based on the clinical features of the disease, we will comprehensively look through genetic, environmental, and immune factors involving in molecular and immunological compatibility pathogenesis, and also generalize common pathological features, such as immune complex deposition and accumulation of lymphocytes. We will also investigate the association and differences between the diseases with comorbidity, and explore the outcome and prognosis of comorbidity of autoimmune diseases. With clarify of the concept of autoimmune comorbidities, we hope bring more and more attention on this aspect, so as to improve the diagnosis, treatments as well as the prognosis of these diseases.