Abstract: Photosynthetic characteristics in oats leaves were measured under Saline-alkali stress in use of the simulated photosynthetic radiation (SPR). The results showed that photosynthetic rate (Pn) increased under slight saline-alkali stress, and with the increase of salt concentration, photosynthetic rate (Pn) decreased. The inter-cellular CO2 concentrations (Ci) and the transpiration rate (Tr) decreased with the increase of salt concentration. Water use efficiency (WUE) under serious saline-alkali stress increased.