Abstract: Photosynthesis characteristics and productivity of Stipa bungeana were studied.The results show that in the early period，Stipa bungeana grow slowly，then from the early May to the early July，it does fast.Its height can reach 92.2cm and the maximum of its daily increased height is 1.67cm.The seasonal dynamic of biomass is a single-humped curve and reaches the top in August and the non-photosynthesis occupies the more proportion.Due to the environmental influence，photosynthesis and transpiration change regularly and their daily variations can be expressed as a two-humped curve.The‘midday reduction’of photosynthesis rate is limited by stomatic and non-stomatic factors.