Abstract: To clarify the regulatory effects of different post-thinning retention densities on stand growth,timber size class structure and carbon stock of near-mature Chinese fir plantations,and to select the optimal retention density corresponding to diverse forest management objectives,this study took 18-year-old Chinese fir plantations at Fujian Shaowu Weimin State-Owned Forest Farm as the research material.A completely randomized block design was applied,with three thinning retention density treatments set at 600,900 and 1050 stems·hm^-2.Based on seven consecutive years of continuous field observation,we systematically analyzed how thinning retention density affected stand growth,timber size class composition,as well as carbon storage in the arbor layer and soil layer of Chinese fir plantations.The results indicated that rising thinning retention density induced declining growth in individual tree DBH(diameter at breast height),tree height and stem volume;conversely,stand growing stock,large-diameter timber yield,and carbon stock of both the arbor and soil layers exhibited an obvious upward trend.Among all treatments,the 600 stems·hm^-2 treatment maximized the growth potential of single trees and was appropriate for targeted cultivation of large-diameter timber;the 1050 stems·hm^-2 treatment significantly boosted stand growing stock and ecosystem carbon sequestration capacity,achieving simultaneous gains in timber production and carbon sink benefits.