AbstractThe ecotones between Quercus mongolica community and other communities such as Juglans mandshurica, Larix olgensis and shrub in Tonghua , Huadian and Daqinggou were studied by sampling method. The structure and composition of three communities and their ecotones in these sites were analyzed. Species richness index , Simpson diversity index and Shannon-Weiner diversity index of Quercus mongolica community , Juglans mandshurica community , Larix olgensis community and their ecotones were calculated. The diversity index and richness index of the ecotones were the highest in Tongha and Daqinggou. But diversity index and richness index of the ecotones in Huadian weren’t the highest due to the absence of strong edge effect . The relationships among the coverage of tree layer ,shrub layer and herb layer were also analyzed.