By using the leaves of bean seedling, we studied the effects of alternative respiratory pathway on the chlorophyll content and the chlorophyll fluorescence characteristics under NaCl stress， to investigate the physiological effects of altemative respiratory pathways under stress and the regulation of photosystem Ⅱ(PSⅡ) in plants under salt stress. The results showed that: (1) the treatment of NaCl with increased concentration (0、100、200、300 mmol/L) caused significant decrease of the chlorophyll content in bean seedling leaves. The ratio of Fv/Fm (the potential maximal photochemical efficiency of PSⅡ), F_v′/F_m′ (the maximum quantum efficiency of PSⅡ photochemistry at illumination), Y(Ⅱ) (effective photochemical quantum yield of PSⅡ photosynthetic), and qP (photochemical quenching coefficient). However, the levels of NPQ (nonphotochemical quenching) were significantly decreased. Meanwhile, the capacity of the alternative respiratory pathway was increased significantly. (2) The NaClstressed leaves, which were pretreated with salicylhydroxamic acid (the specific inhibitor of the alternative respiratory pathway, SHAM), exhibited lower levels of chlorophyll content, F_v/F_m, F_v′/F_m′, Y(Ⅱ) and qP, but higher levels of NPQ than the leaves subjected to NaCl stress alone. These results suggested that NaCl stress can cause a decrease of the photochemical efficiency of photosystem Ⅱ and an increase in dissipation of light energy in the bean leaves, and the alternate respiration pathway could play a role in alleviating the decreas of chlorophyll content and photochemical efficiency of photosystem Ⅱ (PSⅡ) under NaCl stress.