Objective To investigate the clinical effect of pressure dressing at different time points for the prevention of subdural effusion after decompressive craniectomy (DC).Methods A total of 77 patients who underwent DC in our hospital from October 2014 to September 2015 were selected and divided into early group (37 patients) and late group (40 patients) according to a random number table. The early group and late group received bone window pressure dressing at 3 and 7-10 days, respectively, after DC, until the brain tissue was restored to the normal anatomical position. The incidence rate of subdural effusion and clinical prognosis were compared between the two groups.Results Three patients in the early group and 5 in the late group died, and the overall score of Glasgow Outcome Scale and length of hospital stay showed no significant differences between the two groups (P>0.05). Seventeen patients in the early group and 8 in the late group experienced subdural effusion, and the late group had a significantly lower incidence rate of subdural effusion than the early group (P<0.05). Both groups experienced a certain degree of reduction in intracranial pressure, which showed no significant difference between the two groups (P>0.05).Conclusions Pressure dressing at 7-10 days after DC helps to prevent subdural effusion, but has no significant effect on clinical prognosis.