Abstract: The variations of leaf traits of Quercus liaotungensis and Acer mono at different life stages along altitude gradient conditions were studied to explore their resource utilization strategies. The specific leaf area (SLA), leaf dry matter content (LDMC), mass-based leaf nitrogen concentration (LNCmass), mass-based leaf phosphorus (LPCmass ) and ratio of nitrogen to phosphorus (N∶P ratio) were measured for adults, saplings and seedlings of Q. liaotungensis and A. mono on different slope positions along the altitude distribution gradient in Dongling Mountains, Beijing. The results showed that: 1) SLA of two tree species at different developmental stages had significant variations on different slope positions, which was larger at the bottom slope than that on the top slope, while LDMC showed an opposite trend, indicating that the changes of slope positions had same impact on leaf functional traits of species at different developmental stages. LNCmass, LPCmass and N∶P ratio showed no significant changes on different slope positions, suggesting that the slope position had little effect on LNCmass and LPCmass. 2) SLA, LDMC, LNCmass, LPCmass of species at varied developmental stages had a statistically significant difference along the altitude gradients, indicating that these leaf traits of two species at varied developmental stages had different response mechanism to altitude changes. The ratio of nitrogen to phosphorus had no significant differences along altitude changes, since in smaller habitat, altitude has little effect on the ratio.