Abstract: The biomass production model and distribution model were improved based on 3-PG model theory, so as the individual tree growth model could be established to achieve the growth forecast of the Chinese fir (Cunninghamia lanceolata) stand. In this study, the diameter at breast height (DBH) and height (H) were used to evaluate and compare the results of the model simulation and field data. It showed that the average analog precisions of DBH and H of the improved model were respectively 95.57% and 91.16%, significantly higher than that of the 3-PG model, whose precisions were 89.4% and 85.18%. The simulation accuracy of the improved simulation model was significantly higher and the simulation results were better.