OBJECTIVE: To explore the value of color Doppler ultrasound in evaluating the therapeutic effects on ankylosing spondylitis (AS) patients. METHODS: Color Doppler high-frequency ultrasound images and blood flow in 30 healthy volunteers and 50 AS patients, changes of high-frequency ultrasound images and blood flow of involved sites in AS patients pre- and after-Etanercept treatments, as well as erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and the Bath AS disease activity indices pre- and post-treatment were compared. RESULTS: Positive rates were significantly different between healthy volunteers and AS patients in terms of sacroiliac joints, Achilles tendon attachments, patellar ligament attachments, and rectus femoris tendon attachments by ultrasonograph (P < 0.05); and the fibular collateral ligament attachments positive rates had no significant difference with those at pre-treatment (P > 0.05). There was significant difference between patients with Bath AS disease activity index (BASDAI) ≥ 4 and those with BASDAI < 4 with respects to peripheral enthesis positive rate, Bath AS functional index (BASFI), patient's global assessment VAS (PGA), nocturnal back pain and general back pain VAS, morning stiffness duration, ESR and CRP (P < 0.05). Positive rates of sacroiliac joints, Achilles tendon attachments, patellar ligament attachments and rectus femoris tendon by ultrasonograph significantly decreased at Weeks 12 and 24 at post-treatment compared to that at pre-treatment (P < 0.05); there was significant difference for patient's BASDAI, BASFI, ESR and CRP at pre-treatment and weeks 12 and 24 post-treatment (P < 0.05). CONCLUSION: Ultrasound can sensitively detect the pathological changes of joint synovium and entheses so that it may be used as a routine method of monitoring diseases in these soft tissues, following up AS patients and evaluating clinical efficacy.