Abstract: The tissue transparency method was used to observe the morphology of oil cells in the leaves of Cinnamomum longepaniculatum(Gamble) N. Chao ex H. W. Li in spring and autumn, and the density and diameter of the oil cells were determined. Cell wall structure of the oil cells was observed with scanning electron microscopy. GC-MS was used to characterize the chemical composition of the essential oils extracted from the leaves of C. longepaniculatumin in spring and autumn.Eucalyptol, α-terpineol, and γ-terpinene content was analyzed by GC. Finally, antioxidant activity of the essential oils was evaluated. The density of oil cells of C. longepaniculatum leaves in spring and autumn was (41±3) and (38±2) per mm², the diameter was (51.87±1.64) and (36.89±2.64) μm, and the cell wall thickness was 1.65 and 0.63 μm, respectively. The extraction yields of essential oils from C. longepaniculatum leaves were 4.45% and 3.09%(based on dry weight) in spring and autumn, respectively. Sixteen types of chemical compounds were identified with GC-MS, and no significant difference was observed in the content of the three main components. The total antioxidant capacity of the essential oils from C. longepaniculatum leaves harvested in spring and autumn was 6.50 and 5.50 U/mL, respectively (40% of Vc), and the IC₅₀ value corresponding to scavenging of DPPH free radicals was 0.2 g/L.