以林分年龄、地位指数SI、林分密度指数SDI为输入变量 ,从模型间的相容性出发 ,建立了杉木人工林可变密度的全林分模型。着重探讨了用Richards方程构造林分断面积生长模型时 ,有关参数与SI和SDI的关系 ,分析了SDI的变化规律 ,采用名义年龄法建立了SDI的动态预估模型 ,最后 ,给出了应用可变密度的全林分模型模拟林分自然生长过程的实例 Taking the stand age, status index SI and stand density index SDI as input variables, the variable standoff model of Cunninghamia lanceolata plantation was established based on the compatibility of models. This paper focuses on the relationship between the parameters and SI and SDI when using the Richards equation to construct the sectional area growth model of forest stand and analyzes the variation law of SDI. The dynamic prediction model of SDI is established by the nominal age method. Finally, An Example of Natural Forest Growth Process with Variable Density and Whole Forest Stand Models