Objective To observe the clinical and CT features of early and later phase in patients with orbital blowout fracture （BOF）. Methods A prospective record and follow-up of 39 patients with orbital BOF were presented with the clinical manifestations and CT signs of early and later phase in First Affiliated Hospital of Zhengzhou University between June 2012 and August 2013. Main causes of 39 patients with orbital BOF were the boxing injury （46%）， followed by traffic accident injury （23%）. Results The ocular findings of earler stage （in a mean 2.9 d）： were visual deterioration in 13 cases （33%）， the periorbital extravasated blood and swelling in 38 cases （97%）， eye sunken ≥2 mm in 6 cases （15%）， eye movement disorder and diplopia in 17 cases （44%）， infraorbital nerve palsy in 15 cases （38%）. The ocular symptoms of later stage （at a mean 34 d） were visual deterioration in 4 cases（10%）， the periorbital extravasated blood and swelling no one， eye sunken ≥2 mm in 26 cases （67%）， eye movement disorder and diplopia in 5 cases （13%）， infraorbital nerve palsy in 2 cases （5%）. The early stage CT signs were the orbital wall fracture in 39 cases （100%）， extraocular muscles thickening in 36 cases （92%）， extraocular muscle gression in 31 cases（79%）， the edge of the extraocular muscle was rough in 33 cases （85%）， nasal cavity hydrops in 30 cases （77%）， orbital pneumatosis and hematoma in 5 cases （13%）. The later stage CT signs were the orbital wall fracture in 39 cases （100%）， extraocular muscles thickening in 36 cases （92%）， extraocular muscle gression in 31 cases （79%）， the edge of the extraocular muscle was rough in 2 cases （5%）， nasal cavity hydrops and orbital pneumatosis and hematoma no cases. Conclusion BOF have some characteristics in early stage such as the periorbital extravasated blood and swelling， clear and sharp of fracture end， rough edge of the extraocular muscle， nasal cavity hydrops and orbital pneumatosis and hematoma. In the later stage BOF have other characteristics such as eye sunken， ambiguous fracture end and smooth edge of extraocular muscle. Knowing these differences and features will be beneficial to the diagnosis， medicolegal expertise and the clinical treatment.