This is a prospective randomized controlled study to evaluated the efficacy and safety of kunxian capsule in treating of patients with early ankylosing spondylitis (AS). The major outcome index is proportion of patients achieving ASAS20 response at week12, and minor outcome indexes include ASAS50 and ASAS70, BASDAI20,BASDAI50 and BASDAI70. The adverse events at any time were recorded to evaluate the safety.