Objective: To analyze the clinical and laboratory characteristics of macrophage activation syndrome (MAS) in children. Methods: Clinical data (the clinical features, early manifestation, laboratory characteristics, treatment, and outcome) of 23 cases of MAS, who came from our hospital, were retrospectively analyzed. Results: The average age of 23 MAS children (including 11 male and 12 female ) was 7.1-year-old. Underlying diseases were Kawasaki disease (1 case), systemic lupus erythematosus (2 cases) and systemic type juvenile idiopathic arthritis (20 cases). The first clinical manifestations were persisting high fever (15 cases), jaundice and fulminate hepatitis (7 cases), hemolytic anemia (1 case). All the MAS children manifested the progressive enlargement of both liver and spleen, or (and) lymph nodes associated with blood system involvement, 4 cases with central nervous system dysfunction, 5 cases with easy bleeding, 4 cases with respiratory system dysfunction such as bronchial pneumonia or respiratory failure, 8 cases with digestive system dysfunction, 1 case with cardiac disease, 1 case with renal disease and 1 case with mumps. One to three series of peripheral blood cells and erythrocyte sedimentation rate decreased. While the serum transaminase, lactate dehydrogenase,serum ferritin and triglycerides increased. Other dysfunctions were coagulopathy and phagocytic blood cells in bone marrow. The treatment protocols were set individually. Application of methylprednisolone and intravenous gamma globulin therapy with cyclosporin A given intravenously or orally were very effective. In spite of 2 cases died, others got recovered. Conclusions: MAS is not only seen systemic juvenile idiopathic arthritis, but also seen in other rheumatic and immunological diseases(Kawasaki disease,systemic lupus erythematosus).MAS is a dangerous disease and can cause systemic multiple organ damage. Sometime severe hepatitis and hemolytic anemia is the first symptom instead of persistent fever. Treatment with intravenous gamma globulin, methylprednisolone and cyclosporine A can improve the remission rate. Early diagnosis and treatment is key to improve prospects of survival.