On the basis of a 35-sample-plot survey in Hunan and Hubei provinces forecasting models to growth loss percentage have been established, that forecasting precisions are as high as or above 90%. they are, y being growth loss percentage and x disease index, y(tree height) = 28. 00( 1 + 32. 0885nomic threshold models, been derived. Because there are not suitable techniques which can estimate the loss value by the disease and producing value per unit growth , the writer has put forward the disease econmic threshold index, x(ET).T) = 15. In addition it is evaluated that the Chinese fir tree volume outside bark loss of China yearly reaches 920574m3 with costs of 230143500 yuan.