Thirty-two dogs were divided into 4 equal groups randomly following experimental traumatic brain injury.Group I,as control,without any treatment after injury,GroupⅡ,Ⅲ,Ⅳ were treated by mannitol,mannitol adding DX 40 and isovolumetric hemodilution(IHD)respectively after injury.Hemorheology,hemodynamic parameters and intracranial pressure(ICP)were monitored at different intervals during the study,Meanwhile the traumatic brains were examined pathologically.The results demonstrated that hematocrit(HCT),blood apparent viscosity at low and high shear rates(η0.512,η51.2).erythrocyte aggregation index(AI),viscous component(η'),elastic component(η''),elastic modules(G') and ICP increased Significantly after brain injury.In group Ⅱ,HCT,η0.512,η51.2,AI-η',η''decreased obviously at 1 hour after therapy,but increased to the level before in jury at 2 hours after therapy.Except for η51.2,the rest of hemorheol logical parameters decreased significantly in group Ⅲ and IV at 2 hours and 8 hours after therapy,While ICP in group IV was lower than that of the other groups at 8 hours after therapy The Study indicated that IHD is particularly effective in lowering blood viscosity,vlscoelasticity and erythrocyte aggregation,IHD does not result in an increase in cardiac output or ICP,IHD can lead to reduction in cerebra vascular resistance and increasing blood volume in microcirculation and can reduce cerebral edema and the extent of brain damage.We suggest that it is important to examine HCT during the routine treatment of traumatic brain injury and IHD is one of the safe,acceptable and effective therapies in the treatment of brain injury.