Objective To explore the effects and toxicity of repeated administration of wall-removed Ganoderma lucidum spore powder for 6 weeks on the development of various systems in juvenile rats. Methods One hundred twenty- eight juvenile SD rats aged 24 days (postnatal day, PND24) were divided into vehicle control, low-dose, medium-dose and high-dose groups by the weight balance method . Each group was composed of 32 rats ( half male and half female), and received pure water or wall-removed Ganoderma lucidum spore powder 0. 8, 1. 8 and 4. 0 g / kg doses by gavage, respectively, each in a volume of 10 mL/ kg, once a day for 6 consecutive weeks (42 d). The day after drug withdrawal and 4 weeks after drug withdrawal, 10 / 16 and 6 / 16 rats in each group were necropsied, and routine toxicity indicators and indicators of growth and development, bone development, behavior, sex hormones, immune system development, and other indicators were detected. Results Each dose of wall-removed Ganoderma lucidum spore powder had no significant toxic effects on the clinical symptoms, weight, food intake, sexual development, behavior, hematology, serum biochemistry, ophthalmology, growth hormones, sex hormones, skeletal system development, immunology, histopathology, or other indicators of juvenile SD rats. However, the rats in the high-dose group had reversible abnormalities in some urine indicators ( all returned to normal after 4 weeks of drug withdrawal), which was considered to be related to the urine excretion of the test product components or their metabolites. In the water maze test of each dose group, the incubation period decreased, and the percentage of time in the target quadrant, as measured by space exploration, increased, suggesting that the learning and memory ability was enhanced, which may be related to its pharmacological effects. Conclusions Wall-removed Ganoderma lucidum spore powder has no obvious toxic effects in juvenile SD rats, and the NOAEL was 4. 0 g / kg.