In order to reveal the physiological response and adaptive mechanism of Corylus chinensis to light intensity, five different shade intensities (full light (CK), 30%, 50%, 70%, and 90%) were set up to study the effects of different light intensities on the growth morphology, leaf traits, photosynthetic characteristics and chlorophyll fluorescence characteristics of Corylus chinensis seedlings. The results showed that: (1) Seedling height, ground diameter, and total biomass all increased and then decreased with the increase of shade, moderate shade (30%-50%) significantly promoted seedling growth, while root biomass and root-crown ratio gradually decreased with the increase of shade. (2) Leaf area, leaf length, and leaf width all increased firstly and then decreased with the increase of shade degree, and the anatomical structure of leaves (thickness, thickness of palisade tissue, thickness of spongy tissues) under the CK treatment showed the characteristics of sun leaves, and at the same time, decreased with the increase of shade intensity, which showed a certain degree of plasticity. (3) The net photosynthetic rate (Pn), light saturation point (LSP), light compensation point (LCP), and dark respiration rate (Rd) of Corylus chinensis first increased and then decreased with the increase of shade, and the overall moderate shade was higher; the daily changes of Pn and stomatal conductance (Gs) in 0%-70% shade were generally a ‘bimodal curve’ with a midday depression, while 90% shade showed a ‘single-peak curve’. (4) Shade treatment significantly increased the maximum photochemical efficiency of photosystem II (Fv/Fm), the potential activity of PSII (Fv/F0), probability that an electron moves further than QA (Ψo), quantum yield of electron transport (φEo), whereas the quantum yield of energy dissipation (φDo) on the other hand, gradually decreased with increasing shade level. In summary, the optimum light conditions for Corylus chinensis seedlings were 30% to 50% shade, which resulted in the best growth performance, maintenance of high photosynthetic efficiency, and the highest biomass accumulation.