Abstract: This paper analyses the relationship between the seed output,and quality of seed stand of Pinus yunnanensis and the capony density of seed stand through an eight-year experiment on Baima River Forest Farm.The experiment result showed that it was an important method to improve the seed output and quality of seed stand of Pinus yunnanensis by means of thinning and transforming the selected elite stand of Pinus yunnanensis.When the canopy density of seed stand remained 0.4,the seed output which was the best harvest was 2.53 times as much as the contrast stand,1.48 times as much as that of 0.5,and 1.86 times as much as that of 0.6 in canopy density.Meanwhile,the seed quality of the first kind was also the best.In this case,the condition was most beneficial to tree growth of seed stand.This set of methods in thinning management of seed stand of Pinus yunnanensis is worth introducing to the Forestry Department for wide application.