A study was conducted in rats to observe the subchronic toxicity of ethanol extract of Semen Cassiae. 120 Wistar rats were randomly divided into 6 groups (i.e. the negative control group and five treatment groups), and each group consisted of 10 males and 10 females. The animals were given the extract mixed into the fodder of the concentration of 5, 15, 25, 35, 45 g crude herbal medicine/kg BW for 90 days. The results showed that the ethanol extract of Semen Cassiae increased the ratio of kidney/body weight and liver/body weight, made pigment sediment in kidney, colon, rectum, mesenteric lymph nodes and testicle, and reactive hyperplasia of mesenteric lymph nodes. In 15 0 g/kg BW and above dose groups, The increases of spleen/body weight ratio and the number of WBC, and superficially catarrh in colon were found. In the 25 0 g/kg BW and higher groups, the body weight increased slowly, the food efficiency declined and the testicle shrinked. The target organ were kidney, colon, rectum, mesenteric lymph nodes and testicle. The results indicated that the observed adverse effect level of Semen Cassiae ethanol extract was 5 0 g crude herbal medicine/kg BW, and ADI is less than 3 0 g/kg if deduced from rats to human, according to 100 times safety coefficient .This ADI was far below the 9 0 g of suggested dose agreed by codex. When the Semen Cassiae, was used as a component of health food, the dose and term of taking Semen Cassiae should be restricted due to its safety risk ,and it may be irrational to list Semen Cassiae on the materials of health food.