Objective: To investigate the action mechanism of Danshen injection on red blood cell deformability in aged rats. And the change in hemorheological indexes and cholesterol in erythrocyte membrane was studied. Method: Thirty Wistar rats (70-72 weeks old) were randomly assigned to Danshen injection high-dose group (4.4 g ·kg-1)

low-dose group (1.1 g ·kg-1) and model group with 10 rats in each group. Another ten younger Wistar rats were as young control group. The related indexes of hemorheology

such as the whole blood viscosity

plasma viscosity and the red blood cell deformability

were determined while the contents of cholesterol in erythrocyte membrane were determined by HPLC after giving medicine 14 days by intraperitoneal injection. Result: Compared with the model group

the Danshen injection group was effective. The whole blood viscosity (P<0.01)、plasma viscosity (P<0.05) and the content of cholesterol in erythrocyte membrane (P<0.01) were decreased. And the deformability of erythrocyte (P<0.01) was increased. Conclusion: Danshen injection can decrease the content of cholesterol in erythrocyte membrane and affect the metabolism of lipid which maybe one of the mechanism of increasing deformability of erythrocyte and improving the blood viscosity.