The research on the radial variations of forest trunks provides us with more details of forest trunks growth and its relationships with various environmental factors, which enables us to accurately assess how forest ecosystem productivity responds to climate change to quantify the dynamics of forest ecosystem in the future. Previous studies on tree radial growth in China mainly focused on temperate and tropical regions, which were based on coarse temporal resolutions-tree annual rings method. However, there is a lack of studies on radial variations of forest trunks based on high temporal resolution. Therefore, in this study, dendrometer was used to continuously monitor the tree-radial dynamics of Masson's pines in the subtropical regions for 13 months to explore the patterns of tree-radial growth and its response to environmental factors at different time scales. The results showed that:(1) on the diurnal scale, the radial variation of the Masson's pine appeared it contracted during the day and expanded at night. Meanwhile, the expansion of radial at night in autumn and winter was less obvious than in spring and summer. (2) On the seasonal scale, the radial growth of Masson's pine could be divided into four periods(start growth season, rapid growth season,slow growth season and shrinkage season). March-August was the main growth period, and April was the period with the largest cumulative growth. (3) On the daily scale, the relative humidity and water vapor pressure deficit were the main climatic factors to regulate radial variations of Masson pine; on the seasonal scale, soil temperature had a greater influence on trunks' radial variation than that of air temperature. The effects of soil temperature on the trunks' radial variation were different among periods. In the start growth season and the slow growth period, there was a positive and negative correlation between soil temperature and trunks' radial variation, respectively, but in the rapid growth season, no correlation between soil temperature and trunks' radial variation can be found. However, the correlation of water conditions gradually increased over time, and the promoting effect of water factors such as precipitation and relative humidity on the radial growth of trunk was more obvious in the middle and late growing season. The results can help us further understand the radical changes in tree trunks and their response to the environmental changes in subtropical monsoon climate regions. These efforts will provide a basis for reforestation design and sustainable forest management in subtropical regions against the background of climate change.