Litter decomposition is one of the key ecological processes in forest ecosystem, which plays an important role in ecosystem productivity, nutrient cycling and the formation of soil organic matter. In alpine ecosystem, freeze-thaw cycle and snow cover play an important role of litter decomposition processes. Climate change has changed the snow cover and circulation pattern of soil freezing and thawing in the alpine area, however, it could cause timberline upward shift and a trend for a shrub expansion, which will change community structure and species composition in the alpine region. Alpine timberline ecotone indicates the limit distribution of the forest and is a sensitive area of global climate change. From alpine coniferous forest to alpine shrub meadows, different vegetation types on snowfall distribution may cause dramatic variations in snow depth and snowmelt timing, soil temperatures and freezing depth in ecosystem, which in turn control litter decomposition process, and subsequently influence carbon and nitrogen cycle in alpine ecosystem. Rhododendron lapponicum is one of constructive species or dominant species in alpine/subalpine of western China, which was common in the fir forest and alpine scrub meadow. We present here one year study of R. lapponicum leaf litter decomposition in snowing season and growing seasonin alpine timberline ecotone located in the eastern Tibetan Plateau, China, where the ground is completely covered with snow for 5-6 months each year. A field experiment using litterbag method was carried out in different vegetations along an elevation gradient in an alpine timberline ecotone, mass loss, nutrient release and changes of leaf litter were studied. The results showed that: 1) both seasonal variation and vegetation type had significantly effects on leaf litter decomposition of R. lapponicum. Mass loss mainly occured in the growing season and showed the highest value in timberline compared with other vegetations. This may be relatively higher average temperatures in the growing season than snowing season, and there were the most dramatic temperature fluctuations and most frequent freeze-thaw cycles in the timberline. However, slightly higher mass loss in coniferous forest was observed in snowing season compared with that in growing season. 2)Litter mass loss (9.62%) was relatively slow with a coefficient k (0.145) in the first year decomposition in alpine timberline ecotone. 3)Change in quality of leaf litter was mainly reflected in a significant cellulose degradation that concentrated in snowing season, but not significantly degradation of lignin of R. Lapponicum. The C/N, C/P, lignin/N ratios changed little and C, N, P release performed stable and sustainable as the first year decomposition process in the timberline. The results suggested that seasonal snow cover do not only affect litter decomposition in the period of snowing season, but may further accelerate leaf litter decomposition of R. lapponicum in the beginning of the growing season according to frequent freeze-thaw cycles and snow melting in the alpine timberline ectone. In conclusion, with the reduction of snow cover, extension of growing season and the expansion of shrub community as R. lapponicum, would accelerate the litter decomposition of R. lapponicum in alpine timberline ecotone in the scenario of climate warming.