objective? To explore the effect of modified decompressive craniectomy on brain metabolism and cerebral perfusion in patients with severe traumatic brain injury. Methods? A total of 124 patients with severe traumatic brain injury admitted to the Jining NO.1 People's Hospital from April 2018 to September 2020 were selected, according to the random number table method, they were divided into control group and treatment group, each with 62 cases. The control group used conventional decompressive craniectomy, the patients in the treatment group were treated with modified decompression craniectomy. The Glasgow Coma Index (GCS), Mini-Mental State Examination Scale (MMSE)scores before and 7 days after operation, internal jugular vein-radial artery lactate difference (VADL), cerebral perfusion pressure (CCP) levels before and 24 h after operation, the occurrence of complications 7 days after operation, and the prognosis before discharge were compared between the two groups. Results? Compared with before operation, the GCS, MMSE scores 7 days after operation and CCP levels 24 h after operation of the two groups of patients increased, and the treatment group was higher than the control group; compared with before operation,the VADL of the two groups of patients 24 h after operation decreased, and the treatment group was lower than the control group; the total incidence of complications of the treatment group was lower than that in the control group; the proportion of patients in the treatment group who recovered well was 50.00%, which was higher than 30.65% in the control group, while the proportion of patients with poor prognosis was 32.26% in the treatment group, which was lower than 58.06% in the control group (all P<0.05). Conclusion? Modified decompressive craniectomy can improve the brain metabolism and cerebral perfusion in patients with severe traumatic brain injury, promote the recovery of coma, and improve the cognitive function and prognosis of patients.