Objective. To study the effects of active fractions from Lycopus lucidus (L. F04) on erythrocyte rheology so as to investigate its mechanism of promoting blood circulation and removing blood stasis. Method. The effects of L. F04 on erythrocytes deformability, aggregation, liquidity of membrane were examined in the present study and the blood stasis animal model of rats made by injecting high molecular weight dextran (HMWD) was used. Result. HMWD injection decreased red blood cells deformability (P<0.05) and liquidity of membrane (P<0.01) and increased erythrocytes aggregation (P<005). Compared with the model, both L. F04 0.612 g/kg and 0.306 g/kg improved red blood cells deformability (P<0.05), inhibited erythrocytes aggregation (P<0.05), and showed the trend of improving liquidity of membrane. But there was no concentration-dependence. Conclusion. L. F04 can significantly improve the deviant erythrocyte rheology characteristics.