The relationship between plant and environment is always one of key issues in the field of ecology. Attentions have been paid to plant functional traits and the responses of some traits to environment have been found since 19^th century. Many researches at different scales have proved that plant functional trait, especially leaf functional trait, is a useful tool for linking plant and environment. However, the relationships among plant functional traits are more stable and more meaningful than the relationships among the traits and environment. Study on the responses of plant leaf functional traits and the relationships among them to altitude gradients is helpful to know how plants responding and adapting a changing environment. Foliar traits on photosynthesis, diffusional conductance to CO₂ (including stomatal conductance (g_s) and mesophyll conductance (g_m)), carbon isotope ratio (δ ¹³C), nutrient content and morphology of Salix dissa shrub in four sites with different altitudes (2350m, 2700m, 3150m and 3530m) from Balang Mountain were measured and analyzed in order to understand how leaf functional traits and the relationships among them of the species responded to altitudinal gradients. The results showed that leaf nitrogen content per area (N_area), maximum rate of carboxylation (V_cmax) and maximum photosynthetic rate (A_max) increased with decrease of air temperature and air pressure along with altitude increasing. It was likely the response of the deciduous shrub to shorter growing season at higher altitude. However, photosynthetic nitrogen use efficiency (PNUE) and specific leaf area (SLA) decreased with altitude probably because S. dissa allocated more and more nitrogen to non-photosynthetic system, such as cell wall and so on as a kind of adaptation of plants to severe environment. Diffusion conductance (g_s and g_m) and carboxylation capacity were main factors on foliar carbon isotope discrimination, but V_cmax had more important effect on leaf δ ¹³C than diffusion conductance did. It resulted in leaf δ ¹³C of S. dissa increasing with altitude. It was obvious that allocation of nitrogen between photosynthetic system and non-photosynthetic system was a key factor on the adaptation of S. dissa to a changing environment at different altitude Balang Mountain.