Abstract: In order to analyze structures and characteristics of diameter classes, tree heights, basal areas and important values (Ⅳ), etc., the investigation was conducted in a 10-year-old Pinus yunnanensis plantation which established by uneven row spacing of the 1 m ×2 m ×5 m at Jianshan Forest zone of Lufengcun Forestry Farm. The results showed as followings: mean diameter at breast height (DBH) of the stand was 8.3 cm with the DBH ranges of 1.7-14.7 cm, among the DBH range, tree stem sequence (TSS) of the 5.0-11.0 cm was 83.3%, based on 2 cm as a diameter class (DC), the TSS of the 8 cm and 10 cm DC had 2/3 in total stand trees, it was presented normal distribution between the TSSs and different DCs. Mean height of the stand was 4.5 m with mean ranges of 2.6-5.3 m for the different DCs, there was linear regression equation of y=1.891ln (x) + 0.593 3 between the height and the DBH. Total basal areas and the IVs of the different DCs were 4.3-2 057.3 cm² and 0.2%-23.0%, respectively, which also presented normal distribution with the DCs. According to the differentiation of the stand DBHs and heights, it was proposed that the first time tending thinning should be implemented.