Based on the annual mean temperature and precipitation data at the 38 meteorological stations over Tibet from 1971 to 2005,the net primary production(NPP) is computed by Thornthwaite Memoriai Model.The spatial distributions,interannual and interdecadal variations of the NPP are analyzed,and the influences of climate changes on NPP are discussed.The results show that the distribution of NPP is characterized by a remarkable regional feature,i.e.decreasing from the southeastern to the northwestern of Tibet.During last 35 years,the reduction of NPP was insignificant in southwestern Ngari district and Nyalam county,and it ranged from 11.9 to 314.2 kg·hm^-2·(10a)^-1,with the largest in Purang county.In other districts of Tibet,NPP has increased and the increment ranged from 26.8 to 459.8 kg·hm^-2·(10a)^-1,with the largest in Lhasa.Also,the results show that NPP has increased interdecadally in Nyingri district,northern Chamdo district and Nakchu district,but decreased in southwestern,Nyalam county and Gyantse county.On an average over the whole Tibet,the NPP changed interdecadally.When the cold and dry climate occurred in the 1970s,the NPP was lower;and when the warm and wet climate appeared in the 1990s,the NPP was higher.Under climate change scenarios,the warm and wet climate would benefit the NPP with an average increment of yield by 6% to 13% over Tibet,while the cold and dry climate would have an adverse impact on NPP with an average reduction of yield by 6% to 14%.The future climate over Tibet would become warm and moist,and the NPP would also increase by 11% to 26% in 2050.