Objective To research the possible mechanism of Dachaihu Decoction（Major Bupleurum Decoction）for atherosclerosis（AS）.Methods Fifty rabbits were randomized into the blank group

model group

Xuezhikang group

prevention group and treatment group

with 10in each.The AS rabbit models were established by giving high fat diet for 6weeks.The blank group and model group were gavaged with 20ml normal saline（NS）.The Xuezhikang group was gavaged with 20ml Xuezhikang（0.8g crude drug）.The prevention group was gavaged with 20ml Dachaihu Decoction（7.5g crude drug）.Each group mentioned above was given intragastric administration once daily from the 1st week to the 10th week.The treatment group was gavaged with 20ml NS once daily from the 1st week to the 6th week and 20ml Dachaihu Decoction（7.5g crude drug）once daily from the 7th week to the 10th week.The aortic pathology was observed with light microscope.The serum lipid levels

C-reactive protein（CRP）contents and interleukin-8（IL-8）mRNA expression were detected.Results Pathology showed the plaque area and thickness in the prevention group and treatment group were smaller than those in the model group and with less foam cells and inflammatory cell infiltration and no necrosis and scarring in the plaque.Comparing with the model group

the serum lipid levels

CRP contents and IL-8mRNA expression were significantly decreased in the Xuezhikang group

prevention group and treatment group（P<0.01）.The prevention group was superior to the treatment group in reducing serum lipid（P<0.01）.The prevention group was superior to the Xuezhikang group in reducing CRP level and IL-8mRNA expression（P<0.05or P<0.01）.Conclusion Dachaihu Decoction can obviously decrease serum lipid and delay plaque formation by inhibiting IL-8expression and reducing inflammatory cell infiltration.