Plant functional trait has been a hot topic in ecological research in recent years. Of which leaf functional trait is most closely related with biomass, resource acquisition and utilization, and resource use efficiency of plants. In this study, relationships among different leaf functional traits and between leaf functional traits and topographic factors were studied in Mt. Dongling of Beijing, and comparisons of leaf functional traits were made among different forest communities. Pearson Correlation analysis showed that leaf dry matter content (LDMC) was negatively correlated with specific leaf area (SLA),leaf nitrogen content (LNC),leaf phosphorus content (LPC)and leaf kalium content (LKC); Leaf size was positively correlated with leaf thickness; SLA had positive correlation with LNC, LPC and LKC; LNC had positive correlation with LPC and LKC; LPC was positively correlated with LKC. Based on grey relational grade analysis, elevation was the most influential topographic factor for leaf size, LNC and LKC; LDMC and leaf thickness was most affected by steepness of slope; and slope position affected SLA and LPC the most. According to the SLA and LDMC of tree layer, the five communities can be classified into three groups: the first group consists of Betula dahurica and Populus davidiana, the second group contains mainly Quercus liaotungensis, and the third group consists of Juglans mandshurica and Tilia mandshurica. The community classification is consistent with the classification by dominant plants of the zonal vegetation, LDMC and SLA are the leaf functional traits that reflect the differences between communities best.