Abstract: In this thesis, modebuilding mechanism of extension classified prediction was analyzed for natural unevenaged stands′ average growth rate, and the element mode of extension classified prediction was built. Meanwhile, the average growth rates were predicted with the model. The results showed that the method had high prediction accuracy, and was feasible to determinate natural unevenaged stands′average growth rate. Using the stand growth rate with extension classified prediction to determine the selective cutting cycle, which was an index of income approach in the natural unevenaged forest assets evaluation, was the improvement of income approach.