The impact of salinity on three arboreal mangrove plants, Sonneratia apetala(Sa), S. caseolaris(Sc), Rhizophora stylosa(Rs) was studied. The three mangrove species were treated with different salinity levels over a 3 months period. The response and adaptation of these three mangrove species to linity were shown to be different. Net photosynthesis rate, stomata conductance and transpiration rate of leaves decreased and soluble sugar content of leaves increased with salt concentration in all three mangrove species. The MDA content in stems and leaves of Sa and Sc was somewhat decreased when the linity was lower than <10, but rapidly increased with increased salt concentration. The MDA content in stems and leaves of Rs increased only when salinity was greater than 40. Changes of MDA content in roots of the three mangrove species were not observed. The adaptabilities of Sa and Sc to salt tolerance were limited. The more salt tolerance mangrove Rs likely eliminated the free oxygen radicals through the increase in activity of superoxide dismutase (SOD). Results of this experiment identified salinity levels best suited for growth and metabolism of the species providing information needed for maintaining mangrove forestation along the South China coast.