Yiqi Huoxue Oral Liquid(YHOL) was a formula with Qi Reinforcing and bind-circulationactivating actions consisting of Radix Astragali seu Hedysari,Heada,Radix Ilicis Pubesceatis,etc,To study its Pharmacological mechanism, the effects of YHOL on cerebral edema and ultra- struture of cereblal ischemic rat model after reperfusion were observed. The results showed that YHOLdecreased the water content of ischemic barn to some extent, alleviated the neurological symptoms andreduced the damage of brain ultrastructure in the early stage of reperfusion. It is indicated that YHOLcan reduce cereblal edema by protecting the fumction of vascular endothelial cell and the integrity of basicmembranes and improving microcirculation, and exerts a protective effect on the delayed death of neuron.This will Provide an experimental evidence for the clinical application of YHOL.