Objective To explore the major complications and prognosis of patients with severe traumatic brain injury (sTBI) who underwent decompressive craniectomy (DC).Methods 48 patients with sTBI after DC were analyzed retrospectively. We present a modified method of measuring external cerebral herniation. The incidence rate and thickness of external cerebral herniation at different post-operative time were measured. We also recorded the incidence rate and position of expansion of intracranial hematoma or/and brain contusion and cerebral infarction. In addition, preoperative GCS score and 6-month GOS score were involved in the analysis.Results External cerebral herniation secondary to decompressive craniectomy occurred in 37 of the 48(77%) patients with sTBI,, and the most significant degree appeared in the 14th day post-operation. 58.3% patients suffered expansions of intracranial hematoma or/and brain contusion, which occurred in the operative area, the ipsilateral nonoperative area and even the contralateral area. The incidence rate of cerebral infarction was 12.5%, which were all found in operative side. According to the 6-month GOS scores, the mortality rate was 10.4%, and 56.2% patients had unfavorable outcomes (long-term coma or vegetative state 16.7%; severe disability 39.5%),while the rate of favorable outcomes was 33.4% (moderate disability 16.7%; good recovery 16.7%).Conclusions The patients with sTBI may get decreased mortality by decompressive craniectomy, but still have high incidence of vegetative state and severe disability. This suggests that this surgery should be carried out under careful consideration.