Abstract: Analysis was made on the diameter structure of Pinus densata natural forest in ShangriLa County, Yunnan Province. The diameter distribution of the forest was drafted with three distribution functions, i.e., Meyer distribution, Weibull distribution and Logistic distribution, and then Chi square statistics test was applied for the three types of distribution. The results showed that the Meyer negative exponential distribution function fitted the best to express the structure of diameter distribution of P. densata forest, which could be used to predict the diameter distribution structure of the natural stands of P. densata tree species.