Objective To investigate the risk factors and preventive measures for acute epidural hematoma after posterior thoracic spine surgery.Methods A retrospective study of 14 patients who developed acute epidural hematoma after thoracic spine surgery from May 2002 to May 2012 was conducted.There were 6 males and 8 females,aged from 41 to 69 years (average,61.2 years).There were 10 cases of thoracic spinal canal stenosis,3 cases of thoracic spinal meningioma,and 1 case of thoracic metastasis.About 3-14 h (average,6.6 h) after posterior thoracic spine surgery,the neurological deterioration was found,and according to the American Spinal Injury Association (ASIA) classification,there were 5 cases of grade A and 9 cases of grade B.The neurological function before evacuation of hematoma was compared with that after evacuation of hematoma and that at final follow-up.The correlations between hematoma compression time,neurological improvement rate and neurological function before evacuation of hematoma were statistically analyzed.Results After evacuation of hematoma,the ASIA classification of 14 patients was as follows:grade B in 1 case,grade C in 2 cases,grade D in 4 cases,and grade E in 7 cases.The hematoma compression time of 3 patients with grade B or C was more than 10 hours.Obvious difference of neurological function was found before and after evacuation of hematoma.The neurological improvement rate was 63.7％±23.3％ after evacuation of hematoma,which was negatively correlated with hematoma compression time and positively correlated with preoperative neurological function.The neurological function before evacuation of hematoma was significantly different from that at final follow-up.The neurological improvement rate was 86.97％±17.58％ at final follow-up,which was negatively correlated with hematoma compression time and positively correlated with preoperative neurological function.Conclusion The acute epidural hematoma after thoracic spine surgery could cause severe neurological deterioration.The neurological improvement was negatively correlated with hematoma compression time.Evacuation of hematoma must be done as soon as possible once progressive neurological deterioration is found.