Infliximab arm：Infliximab with MTX treatment: Infliximab 3mg/kg at week 0, 2, 6 and then once every 8 weeks, MTX>7.5mg per week. To observe the results at week 14, 30, 54 and 102 after 6 times IFX treatment. It recommended that continue to receiving IFX treatment after remission for a period of time in good economic condition patients while receiving MTX with hydroxychloroquine(HCQ) or leflunomide(LEF) in poor economic condition patients.