Abstract: Based on the background of pine wilt disease posing a serious threat to subtropical Pinus massoniana forests, enhancing their ecological functions through scientific management has become a key research topic. This study focused on P. massoniana stands infected by pine wood nematode in Suichang County, Zhejiang Province. In 2017, 20 permanent monitoring plots were established in two forest types: pure pine forest and pine-broad-leaved mixed forest. Thinning and transformation were implemented at different intensities (40% for pure pine forest and 30% for pine-broad-leaved mixed forest), with untreated plots as the control. Through 8-year monitoring, the effects of thinning on stand structure, biodiversity, carbon sequestration and soil properties were systematically evaluated. The results showed that: (1) After thinning, the total tree density in two forest types significantly increased to 2 149 and 2 590 trees·hm⁻², respectively. The dominant species shifted from P. massoniana to Lithocarpus glaber (Fagaceae), indicating a successional trend toward mixed pine-broad-leaved forest with simultaneous improvements in species richness and evenness; (2) The average diameter at breast height, tree height, height to the first live branch and crown width of trees in the thinned plots were significantly greater than those of the control, reflecting the improved light conditions within the forest; (3) The species composition of the understory shrub and herb layers became notably richer with the addition of species such as Dicranopteris pedata, Rhaphiolepis indica and Callerya dielsiana; (4) The ecosystem carbon storage increased significantly, reaching 112.68 t·hm⁻² in the transformed pure pine forest and 126.95 t·hm⁻² in the mixed forest, representing increases of 26.3% and 32.7%, respectively; (5) Soil acidification was alleviated, and the contents of nutrients such as organic carbon, total nitrogen and available phosphorus were significantly increased, indicating the improvement of soil ecological functions.Therefore, moderate thinning and transformation can effectively optimize stand structure, promote biodiversity recovery, and synergistically enhance carbon sequestration capacity and soil fertility, which provides a scientific basis for close-to-nature management and ecological restoration of subtropical pine forests.