 This is a prospective open-label study to evaluated the efficacy and safety of infliximabRemicade in treating of patients with early ankylosing spondylitis AS. Infliximab was injected intra-venous on baseline, 2nd week, 6th week, 12th week and 24th week, with dosing of 5mgkg. The major outcome index is ASAS20, and minor outcome indexes include ASAS50 and ASAS70, BASDAI20,BASDAI50 and BASDAI70. And MRI of sacroiliac joint is not necessary. The adverse events at any time were recorded. 