Abstract: Objective To investigate the subacute toxicity of American ginseng lyophilized powder to Sprague-Dawley (SD) rats.Methods Eighty specific pathogen free (SPF) rats were randomly divided into three groups:high,moderate and low dose American ginseng groups (3.00,1.50 and 0.75 g/kg) and a control group.The control group were fed with basal feed and the American ginseng groups fed with the feed mixed by various contents of American ginseng for 30 days.Food intake,weight gain,viscera ratio of the main organs,and the change of food utilization rate of the rats were observed.The rats' routine blood indexes and serum biochemical indicators were detected using blood cell analyzer and biochemical analyzer.Pathological examinations were conducted for main organs of the rats.Results There were no abnormalities in the growth and development of the rats of control group and American ginseng groups;no death and abnormal statuses of mental and physical activity were observed in all the rats.Compared with those of the control group,the rats of American ginseng groups showed no significant differences in body weight gain,food utilization,and functions of main organs.There were no obvious pathological changes in the liver,kidney,spleen,testis or ovary of in the rats of the control group and the high dose American ginseng group.Conclusion American ginseng lyophilized powder is of no significant subacute toxicity to rats.