Abstract: Through analyzing the forest resource changes in Chinaand some other countries and summarizing the rule of economic development and forest resource changes in various countries, the paper puts forward the U-modeltheory to explain the forest resource changes and the rule of the changes and then expatiates the U-Model Theory and points out that the economic development and the policies of forestry development are vital to the process of such changes.

Key words: forest resources, U-model, economic development