Objective To investigate single dose and repetitive dose toxicity of compound Yizhihao particles on pre-weaning Sprague Dawley ( SD) rats ( postnatal day 15; PND15 ) and provide a reference for human clinical use. Methods Five litters of female rats and their offspring were selected that met the requirements of the fostering design. Three litters were randomly divided into solvent control,compound Yizhihao particles dosage groups (70. 4, 88. 0 g / kg), according to the serial numbers of the female rats. A detailed observation of the rat, including examination of viscera morphology by naked eye, was conducted until day 14 post-drug administration. Simultaneously, 20 female rats and their offspring were selected that met the requirements of the fostering design. Each litter was randomly divided into solvent control, lcompound Yizhihao particles dosage groups ( 17. 6, 44. 0, 70. 4 g / kg) according to the serial numbers of the female rats. At PND₁₅ , compound Yizhihao particles was orally administered daily to the juvenile rats for 28 days, with recovery for 28 days after cessation. Parameters were examined including general condition, development index, ophthalmic examination, behavioral test, and histopathological examination. Results In the single dose toxicity study, three animals died in the 88. 0 g / kg dose group at day 2 while the weights of both the 70. 4, 88. 0 g / kg dose groups decreased significantly. In the repetitive dose toxicity study, compared with the solvent control group, the weights of both male and female rats in the 70. 4 g / kg dose group were significantly decreased at day 3. After 28 days of treatment, a decrease in mean crown-rump length and tibia length were noted in the males of the 70. 4 g / kg dose group. Urine bilirubin showed increases in the 44. 0, 70. 4 g / kg dose groups. The ratio of liver and kidney weight to body weight and to brain weight in the 17. 6, 44. 0, 70. 4 g / kg dose groups for both male and female rats were higher than those in the solvent control group. Conclusions The maximum tolerated dose of compound Yizhihao particles in juvenile rats was 70. 4 g / kg in a single dose toxicity study. The no observed adverse effect level was 44. 0 g / kg in a 28 day repetitive dose toxicity study.