To study the effect of ligustrazine injection (LI) on vascular endothelial cell of the patients with arteriosclerosis obliterans (ASO) and explore the new pathway of investigating effective vascular protective agents in Chinese medicinal herbs. Methods: Forty six patients with ASO in the LI group treated by LI were observed, their circulating endothelial cells (CEC) were detected quantitatively before and after treatment. The results were compared with the CEC of 53 cases of healthy persons (control group) in the same period. Results: In the LI group, the immediate cure rate was 45.7% (21 cases), markedly effective rate 36.9% (17 cases) and the effective rate 17.4% (8 cases). The CEC of patients before treatment was 4.39±1.76/0.9μl, which was significantly higher than that of the healthy persons (1.53±0.42/0.9μl). It could be reduced after treatment, along with the improvement of symptoms and signs, to 2.43±0.87/0.9μl, P<0 01. Conclusion: LI in treating ASO not only displays extraordinary effect, but also has good effect in curing the damage of endothelial cells. To study the effect of ligustrazine injection (LI) on vascular endothelial cells of the patients with arteriosclerosis obliterans (ASO) and explore the new pathway of investigating effective vascular protective agents in Chinese medicinal herbs. Methods: Forty six patients with ASO in the LI group treated by LI were observed, their circulating endothelial cells (CEC) were detected quantitatively before and after treatment. The results were compared with the CEC of 53 cases of healthy persons (control group) in the same period. Results: In the LI group, The immediate cure rate was 45.7% (21 cases), markedly effective rate 36.9% (17 cases) and the effective rate 17.4% (8 cases). The CEC of patients before treatment was 4.39 ± 1.76 / 0.9 μl, which was significantly higher than that of the healthy persons (1.53 ± 0.42 / 0.9 μl). It could be reduced after treatment, along with the improvement of symptoms and signs, to 2.43 ± 0.87 / 0.9 μl, P <0.01. not only displays e xtraordinary effect, but also has good effect in curing the damage of endothelial cells.