This paper deals with the law of assimilation organs quantity vertical distribution of Pimis yunnanensis Franch, and the influence caused by different developing ages of plant, the stand density, the slope and the elevation to the law. Mathematical equation was used to describe it. This law will help to understand the effect of the assimilation quantity vertical distribution on population productive ability and the reason for the change of plant diameter growth and the model for the change of vertical distr...