The effects of 3% Cortex Eucommiae extracts on serum lipid contents were evaluated in rats. Forty-two male Sprague-Dawley rats weighing $100{pm}10g$ were divided into seven groups and fed different fat diets for four weeks. Each group was administered with following group: Control, basal fat diet, saturated fat diet and unsaturated fat diet respectively was fed 1% cholesterol, Cortex Eucommiae extracts 3%. The contents of serum lipid contents triglyceride in the basal fat diet group were higher than those of control group. The contents of total-cholesterol in serum of the saturated fat diet group was significantly higher than other group. The contents of HDL-cholesterol in serum of the 3% Cortex Eucommiae extract group were higher than those other fat diet group. The contents of LDL-cholesterol in serum of the 3% Cortex Eucommiae ex1ract group was lower than other fat diet groups. These results suggest that 3% Cortex Eucommiae extract group may reduced elevated levels of serum lipid contents in rats different fed fat diet.