Globally, forests cover 30% of the earth's land area. As an important renewable resource, forest plays an important role in soil and water conservation, biodiversity protection, carbon storage and scientific research. We developed a forest carbon content model to evaluate the carbon content of forests and forest products. We have developed a comprehensive scoring model based on AHP, which can consider different factors that affect the comprehensive value of forest. We introduced a time series model to predict the change of forest carbon content. Finally, we chose Changbai Mountain Forest in China as an example to demonstrate practical application of the three models.