As a kind of typical ecotone,alpine timberline has become one of the major concerns in global climate change studies because of its special structure,function and high sensitivity to climate change. An increased understanding on physiological mechanism of timberline formation is of great importance in forecasting timberline dynamics under future climate change. This paper analyzed the dynamic of alpine timberline on the Mt. Gongga, and treeline ( Abies fabri) radial growth trends and their relationship with climate change. Based on the previous non-structural carbohydrates ( NSC) determination in 3 timberline tree species ( A. fabri,Picea likiangensis var. balfouriana,Quercus semicarpifolia) on the Gongga mountain,the physiological mechanism of the alpine timberline formation were briefly summarized. The results of the combined treelines species showed that the treeline trees may suffer from a winter carbon shortage. The source capacity and the sink capacity of trees influence its tissue NSC concentrations and the carbon balance. The persistence and development of treeline trees in a harsh alpine environment may require a minimum level of the total NSC concentration,a sufficiently high sugar: starch ratio, and a balanced carbon source-sink relationship. The future research should be focused on the long term observation and simulation of alpine timberline dynamics on the regional scale under climate change,physio-ecological adaptation of timberline trees to extreme harsh environment,and long-term monitoring of relationship between the carbon source and the carbon sink in the timberline forest vegetation.