Abstract: The response of gas exchange parameters such as net photosynthesis rate(Pn),transpiration rate(Tr),water use efficiency of leaf(LWUE),stomatal conductance(Gs) and intercellular CO_2 concentration(Ci) of 2-years old Periploca sepium Bunge to different soil water content(SWC) were studied in Loess Plateau with CIRAS-2 portable photosynthesis system.It showed that the diurnal variations of Pn,Tr and LWUE were affected by SWC.The fitting range of relative soil water content(RWC) for higher photosynthesis production and water use efficiency of leaf were 31.6%～84.9%.The lowest RWC for normal physiological growth was about 21.7%.It concluded that the Periploca sepium Bunge,as a alternative shrubbery specie which had wide fitting range of SWC,and could be planted in Loess Plateau especially in the south slope and escarpment.