Yunnan Pine is the predominant woody tree in southwestern China as well as one of important forest resource in China.The paper give a study to Yunnan pine forest in mid-Yunnan province and Weibull distribution were β distribution were used to fit and forecast the diametral distribution regularity of natural and man-made Yunnan pine forest.All distributions were checked by x2 checking method.The results showed that Weibull and β distribution could describe the diametral distribution well.The curves’ measure of skewness is left,and kurtosis value is positive.The curves have the features of high precision and good adaptability.Between them,Weibull distribution’s fitting is better than β distribution and could be used to forecast the yield,woody quantity and to evaluate management.
