Abstract: An experiment was conducted to study the community species composition , diameter class structure and the naturalization trend of larch plantation by using sample plot with net check survey method , community importance value analysis method and diameter class division method. Results show that: along the gradients of slope position from upper to lower, larch predominate in each community (importance value 0.376—0.461), Korean pine occupy the subdominance and present gradually increasing trend(importance value 0.279—0.402), hardwood trees also occupy certain proportion(importance value 0.186—0.290), and all the communities present obvious naturalization trend; proportions of larger diameter class larch reduce(29.79 %—11.32 %) while middle diameter class larch proportions increase(68.08 %—88.68 %), proportions of middle diameter class hardwood trees increase (18.18 %—58.34 %) and small diameter class trees reduce(81.82 %—41.66 %). There is no large diameter class trees exist, proportions of middle diameter class Korean pine increase(7.68 %—15.00 %) while smaller diameter class trees reduce (92.32 %—85.00 %) and no large diameter class trees exist. Therefore, more attention should be paid to cultivating Korean pine and hardwood trees under larch plantation.