Abstract: To investigate the physiological adaptability of mangrove plants under different salinity,the influences of different salinity（0,5%,10%,15%,20%,25%,30%,35%） on the growth of six mangrove species（Bruguiera gymnorhiza,Ceriops tagal,Rhizophora stylosa,Bruguiera sexangula,Aegiceras corniculatum,Kandelia obovata） were assayed,and the morphological and physiological characteristics of six species were determined respectively,including the biomass,plant height increment,base diameter increment,net photosynthetic rate,chlorophyll a content,chlorophyll b content,total chlorophyll content,superoxide dismutase（SOD） activity,proline（Pro） content and malondialdehyde（MDA） content.The results showed that the 5%-20% was suitable salinity for the growth of six mangrove seedlings,and the Parmentiera cerifera had high salt tolerance.The SOD activity,Pro content and MDA content and chlorophyll content of six mangrove seedlings increased,but net photosynthetic rate and growth rate decreased under salt stress.The results showed that the photosynthesis of the six species seedlings decreased under salt stress,the photosynthetic rate increased by increasing the chlorophyll content,and the plant stress resistance might be improved by increasing the SOD activity,Pro content and MDA content in the leaves.