Abstract: This paper attempts to apply the theory of grey system to forest growth prediction and seeks the grey mobile model. When creating the model, the rectified grey model was used according to the physiological law of forest growth. This model is especially suitable to the occasion that the change takes place in system interior. Therefore the scope of grey prediction was extended. At last, the forest growth of coming management-period was forecasted by the rectified grey model. The result corresponded closely to objective reality.