Objective To investigate the effect of intravenous uniform rehydration on hemorheology in patients with moyamoya disease after preoperative water-deprivation. Methods Twenty-seven patients with moyamoya disease who were about to undergo indirect intracranial and extravascular revascularization were enrolled in the study. Fasting blood was taken on the second day of admission for hemorheological examination, which was considered as the control group. After fasting on the night before the operation, patients were given intravenous uniform rehydration until before entering the operating room, and blood was taken again for hemorheological examination, which was considered as the experimental group. Whole blood low-shear viscosity, whole blood medium-shear viscosity, whole blood high-shear viscosity, plasma viscosity, hematocrit, erythrocyte aggregation index, erythrocyte rigidity index, and erythrocyte deformation index were compared between the two groups. Results The whole blood low-shear viscosity, hematocrit, and erythrocyte aggregation index were significantly higher in the control group than in the experimental group (P<0.05), while the erythrocyte rigidity index and erythrocyte deformation index were significantly lower in the control group than in the experimental group (P<0.05). Conclusions Intravenous uniform rehydration after preoperative water deprivation can reduce blood viscosity and improve erythrocyte deformability in patients with moyamoya disease.