Abstract:Taking 258 plots of Larix plantation as the experimental material, probabilitydensity function parameters fitted to Weibull distribution of every plot were calculated.It was found that the parameters increased with increasing of upper height anddiameter, but decreased with increasing of density. Thus, the Richards model extendedrelations between stand factor and parameter, among parameters was established. Thecombination of parameter model with density, upper height, and diameter model wasdetermined the best, after precision, significance, applicability, and the averagediameter of basal area were tested. The tree distribution of a forest stand can bepredicted by the model. And the model can provide the base for intermediate cuttingsat different growth stages and intensities, and predicting stand volume.