The relations among phenolics content, activities of enzymes related to phenolics metabolization and antioxidant activity in leaves of Juglans sigillata Dode. cv.‘Qianhe 7’were explored at different development periods. The results showed: (1) the phenolic acids and flavonoids were the most content compounds of phenolics, and four kinds of enzymes, namely DAPHS, PAL, C4H and 4CL play the important roles in the phenolics biosynthesis. While POD and PPO related decomposition were higher at leaf mature period, and the PPO is responsible for polyphenol oxidation. (2) With the development of leaves, the total polyphenol extract of the leaves showed a decreasing trend on the ABTS and DPPH free radical, while the reduction capacity of PFRAP and PFRAP increased continuously, reaching a peak in early August, and then remained at a high level. (3) With the development of leaves, phenolic acids were positively correlated to activities of PAL, C4H, the content of phenolic acids and flavonoids were strongly correlated to activities of DAPHS. Furthermore, the total contents of phenolic acids and flavonoids were negatively correlated to PPO. (4) The phenolic acids content was significant or extremely significant correlated to four kinds of antioxidant activity, the correlations between PAL, C4H, CHI and antioxidant activity were stronger than those of others EAB. The activities of PAL, C4H and CHI were positively correlated to IC₅₀ values of DPPH and ABTS⁺, and negatively correlated to values of FRAP and PFRAP. While the activities of PPO and POD were negatively correlated to IC₅₀ values of DPPH and ABTS⁺, and positively correlated to values of FRAP and PFRAP.