In the practice of forest ecology, scale transfer was an important key question. Multiple scales distribution of diameter was often came and the better resolved method was not put forward. Multiple scales model built was a better method on this facet, It included 2 contents: firstly, appropriate choice of probability distributions model.This paper used Maximum Entropys theory to educe unite distribution model of diameter,and which could explain causes that certain distribution was obeyed by measurement factors.So it could be unite Probability distribution model on plot scale.Secondly, scales transfer each other.There were 2 disadvantages in generally method that researched scales questions: (1) taking large scale would cause the losses of base plot information, and (2) small scale in stand level is difficult to scale up.In this paper, we applied Maximum Entropys theory to build the united Maximum Entropys Probability function. It overcame generally methods disadvantage.So the united Maximum Entropys function for the probability density sufficiently made use of each Moso bamboo plots information, and realized multiple scales.Finally,this paper used 22 plots of Moso bamboo to verify this method, and results indicated that new model was feasible and estimated precise of each plot was high.