Abstract: Through study on three communities (64 year-old, 100 year-old stand and 270 year-old stand)on Fenglin Nature Reserve, the south slope of Xiaoxing' anling, we discovered that from 64 year-old forest to 270 year-old forest, the coverage and richness of oak ( Quercus mongolica ) decreased gradually and the coverage and richness of Korean pine (Pinus koraiensis) increased gradually. The percentage of adult oak trees was from 75.7 % to 33.2 % and 8.8 %. The percentage of adult Korean pine trees was from 9.1% to 28.1% and 67.4 %. The oak forest was able to turn into pine-broad leaves mixed forest and Korean pine forest under the condition that the oak forests were not disturbed repeatedly by human activity. The species diversity of 100year-old forest among these three communities was the highest. The number of constructive species nearly didn′t change. The average number of trees was the highest in the mixed forest.