The response of altitudinal treelines is considered reliable indicators of the effects of climate on tree growth and forest dynamics in the rapidly changing climate. Demographic response including stand age structure and regeneration potential of tree species in treeline indicate treeline dynamics, and tree ring records of these forests show the growth limiting climatic processes. To find out how do treeline trees respond to changing climate, we studied different tree species (Abies spectabilis, Betula utilis, Abies georgei and Larix potaninii) in Trans-Himalayan zone, Nepal and Hengduan mountain, China. Trans-Himalaya included Chimang and Lete treeline sites, wheras Hengduan region included Tianbao Mountain and Xiangcheng treelines sites. We reconstructed the age structure of tree by counting the yearly formed rings in cross-section of stem, and also by terminal buds count for seedlings and saplings. Limiting climatic factors for tree growth were identified by most closely linked periods of low and high growth in alpine treeline ecotone and proximity of timberline forest. The growth response showed that treeline is moisture sensitive in trans-Himalayan zone, Nepal and is temperature sensitive in Hengduan zone, China. There were abundant seedling recruitment, greater regenerative inertia and colonization with consistent range shift of the A. spectabilis and B. utilis treeline in Nepal, and lower seedling recruitment with lower regenerative inertia but still shifting treelines of A. georgei (Tianbao Mt.) and L. potaninii treeline (Xiangcheng) in China. From our study we concluded that treeline dynamics is driven mainly by temperature and moisture climate, and is also highly sensitive to modifying factors such as microhabitat conditions despite of climatic suitability. Closer examination of belowground environment (soil temperature and moisture), separately to juveniles and adults, as well of detail study of biotic interactions are equally important for making accurate prediction on treeline dynamics to changing climate.