Abstract: The paper aims to study the effects of shading on growth and development and photosynthetic physiological characteristics of Panax japonicus var. major. The authors investigated the botanical characters, physiological index and photosynthetic characteristics under different shading treatments (0%, 30% and 50%) when Panax japonicus var. major grew about 90 days. The results showed that: compared with control, the stem length, stem diameter, fruit number, rhizome diameter, content of chlorophyll, the activity of superoxide dismutase (SOD) and peroxidase (POD) were enhanced under 30% shading treatment, and the internode length of underground stem and malondialdehyde (MDA) content declined; the net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration rate (Tr) under shading treatments were lower than that of the control, while the intercellular CO2 concentration (Ci) was higher than that of the control. Shading treatments effectively alleviate midday depression and reduce the photoinhibition of Panax japonicus var. major, thereinto, 30% shading treatment is the most effective, which provides a suitable environment for the growth of Panax japonicus var. major.