Forest microclimate is deeply affected by the regional water-thermal pattern change and ecosystem succession. So, it needs to be further studied and assessed about the responses and feedbacks of different successional forests to the current climate change. In this study, we focused on three undisturbed forests in the Dinghushan biosphere reserve Pinus massonniana forest (PF), Mixed Pinus massonniana/broad-leaved forest (MF), Monsoon evergreen broad-leaved forest (MEBF), which forming a natural successional sequence in the south subtropical region of China. By analyzing the microclimates in the three different successional forests and their time-series dynamic trends, the changing mechanisms of forest water-thermal environment were explored. Analysis results indicated that: Driven by the succession from artificial planted PF to transitional forest MF to climax forest MEBF, forest air temperature and surface soil temperature both reduced significantly. Contrarily, the relative air humidity and water content of surface soil and litter increased gradually. In the south subtropical region, where rain and heat appears at the same period, the "cooling effects" of the three forests were different. The air temperatures within PF were 7.9% and 3.6% less than the CK in dry and wet season, respectively; Transitional period MF were 11.6% and 6.4% lower, and climax forest MEBF were 15.7% and 10.5%, respectively. On the whole, the forest "cooling and damping effects" had been strengthened over succession. In particular, the "cooling effect" was more prominent in dry season than in wet season, while the "damping effect" was more obvious in wet season. What is more, the later period forest was more advantageous in regulation of maximum air temperature and soil temperature. Seen from the time-series data, the moisture holding ability of forest also declined due to the global warming and regional precipitation pattern change, especially the intensification of rainfall storms and the increasing number of annual no-rain days. Mainly shows that the 0-50cm depth soil moisture of three forests all declined significantly from the year 1984 (P < 0.001), and the average decreasing rate in wet season was faster than that of dry season. Besides, the average decreasing rate of three forest soil moisture presented the follow order in both annual and wet seasons: MF>MEBF>PF, while in dry seasons it was MEBF>MF>PF order, similarly. Finally, although the air temperature, soil temperature of the three forests changed little during the study period, the relative air humidity (P=0.021) and natural water content of litter (P=0.003) of climax community MEBF both decreased significantly. Consistent with the variation trend of soil moisture, the average decreasing rate of relative air humidity and litter water content also presented to be faster in wet seasons than in dry seasons. We concluded that the mature forest tends to be more sensitive and vulnerable to the regional climate and water-thermal pattern change in south subtropical region of China.