Abstract: We investigated leaf traits of Elaeagnus mollis in the Elaeagnus mollis Nature Reserve of Yicheng County, Shanxi Province. Leaf areas were estimated with use of a Li-3000A Leaf Area Meter, and the maximum photosynthetic rate per unit area (A_area) was measured by Li-6400 portable photosynthesis system. N content was measured by the H₂SO₄-H₂O₂ method. We also calculated the SLA, the maximum photosynthetic rate per unit mass (A_mass), photosynthetic N use efficiency (PNUE) and leaf N content per unit mass (N_mass). As well, we analyzed the interaction between them and size classes. With increasing size of E. mollis, SLA, A_area, N_mass and PNUE decreased and then increased. With size of about 7.5 cm, SLA, A_area, N_mass and PNUE reached the minimum value, so the photosynthetic capacity and PNUE were comparatively low under this condition, and the survival pressure became greater. Leaf trait variables of E. mollis are effective targets to study population dynamics changes and are convenient for study.