Abstract: Using different concentration of NaCl treating seedlings, the effects of salinity stress on photosynthesis of cucumber leaves of two breeds, which were different in tolerance on salinity stress, were investigated. The result showed that, as increasing of salinity concentration and prolongation of salinity stress, the .photosynthetic rate, chlorophyll-a content, chlorophyll-b content were decreased significantly, stomatal conductance and and intercelluar CO2 content decreased early and then increased, the ratio of Chlb/Chla were increased gradually. The extent of injury was different between cucumber of two breeds, the injury extent of the cucumber Jinyou3, which has a higher tolerance on salinity, was less than that of Zhongnong15, which has a lower tolerance on salinity.