Abstract: A UV-B-exclusion study was performed in alpine Kobresia humilis meadow during plants growing season. The PSⅡ photochemistry efficiency, photosynthetic pigments and UV-B-absorbing compounds were measured on native alpine plant Saussurea superba. 1) The 3 min dark adapted quantum efficiency of PSⅡ photochemistry, F_v/F_m, showed an increasing trend after a short-term removal UV-B radiation from natural sunlight in all measurements. These means there were photo-inactivation and/or photo-damage of photosynthesis occurred in PSⅡ reaction center. 2)There were same tendency in PSⅡ photochemistry efficiency Φ_PSⅡ and photochemical quenching qP for all measurements during plants growing season; The Φ_PSⅡ and qP were increased and NPQ decreased after removal UV-B treatment, which means that there was an increasing in PSⅡ photochemistry efficiency and a decreasing in non-photochemical quenching and current solar UV-B intensity can impair photosynthetic function. 3)The reduction of photosynthetic pigments contents were mainly caused by the reducing of leaf thickness and relative increase of photosynthetic pigments contents in amb UV-B treatment a specious phenomenon. In summary, strong solar UV-B radiation in Qinghai-Tibet region has a potential negative influence on photosynthetic physiology process in S. superba. UV-B-absorbing compounds were not influenced during the short-term removal of UV-B radiation, mainly due to strong stabilization of these compounds existed in the epidermal layer of the alpine plant S. superba and can provide effective defense against the natural solar UV-B intensity.