Abstract: Objective:To investigate the protective effect of dexamethasone(DXM) with mannitol on acute severe cerebrovascular disease.Methods:patients met the diagnostic criteria were divided into treatment groupand control group.In the treatment group,3 mg DXM 20% mannitol was given intravenously per 4-6 hours,continuous application of 3-5 days,a maximum of 7 days on the basis of routine treatment.The control grouponly received routine treatment.At the same time monitoring intracranial pressure (ICp) was monitered once per hour,until ICpreturned to normal or the patients died.Then tracked them after the first survey at 1,3,6 months respectively,made GCS score again.Results:There was no significant difference in ICpon admission between the two groups(P＞0.05).In the treatment group,ICpreturned to normal in 2-4 days,but in the control group,more concentrated 3-7 days.Compared the number of cases,ICpreturned to normal at the 3,4 days,the difference was statistically significant (P＜0.01).The complications between the two goups showed no statistically significance(P＞0.05).Ten cases were died in the acute phase in the two groups,the treatment grouphad 3 cases,mortality rate was 6%.The control grouphad 7 cases,mortality rate was 14%.In the treatment group,the number of cases with symptoms improved was more than the control group(P＜0.05) in GCS score.The treatment grouphad 3 cases in 7 new deaths.Conclusions:DXM with mannitol can reduce more brain edema,more intracranial pressure and promote the recovery of neurological function than control groupin acute cerebrovascular disease,and does not increase the morbidity and mortality.