Vertical distribution of leaf functional traits is common in natural forest communities. However, how leaf functional traits vary with the vertical canopy height is still unclear. Here, we selected eight common tree species (Pinus koraiensis Sieb. et Zucc, Fraxinus mandschurica Rupr, Juglans mandshurica Maxim, Acer mono Maxim, Quercus mongolica Fisch.ex Ledeb, Carpinus cordata Bl, Betula platyphylla Suk, and Carpinus cordata Bl) from temperate needle and broadleaf mixed forests in Northeast China, and measured six conventional leaf functional traits (specific leaf area (SLA), leaf dry matter content (LDMC), leaf nitrogen content (N), leaf phosphorus content (P), N:P ratio (N:P), and chlorophyll content (Chl)) under nine different canopy heights, to explore the variation of leaf traits with vertical canopy height of the canopy and its underlying mechanisms. Our results showed that:1) leaf functional traits of the tree species were significantly different among the different canopy heights; 2) SLA, LDMC, N, P, N:P, and Chl showed different trends with increasing vertical canopy height. SLA of broad-leaved species decreased, whereas LDMC of all tree species increased as the vertical canopy height increased. Moreover, N, P, N:P, and Chl of different tree species varied with increasing vertical canopy height; 3) there were significant positive correlations between SLA and N, P, N:P, suggesting that higher SLA with higher N, P, and N:P could optimize leaf photosynthesis in the canopy. This study explored the vertical variation of leaf functional traits along canopy height in natural forests and expanded the scope of research on traditional traits. Furthermore, our findings could optimize ecological modeling in the future, to detect canopy height more effectively through the use of remote sensing or radar.