Abstract: Based on the Brink revised formula,a generalized stem form model was established,by which the changes of tree stem of Chinese fir (Cunninghamia lanceolata) plantation can be well described at different sites,densities and ages.Of the generalized stem form model,parameter i is correlated to diameter breast high (DBH) and the value will be larger when the DBH increases;while parameter q is correlated to tree height (H) and the value will be smaller when the H decrease,which verified the conclusion by Gadow,et al.Parameter p is unrelated to both H and DBH and verified the research results by Steingass.Parameter p is weak negatively correlated to density,while parameter q is weak-positively correlated to density.Parameter q is correlated to site and the value will be larger with site index,too.When simulating stem form,the generalized stem form models with bark and without bark should be used respectively.