Abstract:Based on demography of the age structure，survivorship curve and prediction from Leslie matrix model，the dynamic process of the Juglans mandshurica population at J. mandshurica and Fraxinus mandshurica forest, dominant J. mandshurica forest, mixed forest and mixed broadleaf-conifer forest, respectively, in Mt. Changbai of northeast China，was discussed and predicted. The results indicate that age structure of J. mandshurica population belongs to the type of decline, due to the characteristics of seedling and saplings with a small proportion of total population and high mortality rate at early stage, and that J. mandshurica population possibly underwent environmental screening at past 15-20 years. Leslie matrix model predicts basically that population of seedling and total numbers of J. mandshurica population, will have a decreasing trend in next 35 years. Although the population will be increased at dominant J. mandshurica forest, populations of J. mandshurica at the other three kinds of forests will be declined in the future. Therefore, it is essential to promote forest natural regeneration and to foster to seedlings and saplings as well as young J. mandshurica forest rationally.