The influences of different salinity (0、5、10、15、20、25、30、35、40) on the growth of mangrove species, Bruguiera sexangula var. rhynchopetala (Rhizophoraceae) seedlings were studied using the automatic tidal-simulation device in sand culture of greenhouse. The morphological and eco-physiological characteristics of B. sexangula var. rhynchopetala seedlings, e.g. biomass increment, biomass allocation, rate of photosynthesis, leaf chlorophyll content, root activity and other resistance physiological indexes, were determined in this study. The results showed the parameters associated with the height, stem base and blade growth of B. sexangula var. rhynchopetala seedlings varied widely under the treatments with different salinity. With the increase of salinity, the height of seedlings of the B. sexangula var. rhynchopetala decreased; the thickness of stem changed from thin to thick, then to thin again; the blade changed from slender and greenish to roomy and bottle-green, then to small and blackish green. At the same time, the activity of superoxide dismutase (SOD), the contents of proline and malondialdehyde, and the permeability of membrane in leaves decreased first and then increased. The growth rate, organ and total biomass increased at low salinity, but decreased at high salinity. The leaf area was large when the salinity was less than 25. In contrast, the leaf area decreased remarkably when the salinity was more than 25. The chlorophyll content increased first, then decreased, but increased again with the increase of salinity. The chlorophyll content under the treatment of 5-15 salinity was slightly higher than the treatment with no salt, and decreased slightly with the increase of salinity. In contrast, the chlorophyll content increased remarkably when the salinity was more than 30. The net photosynthetic rate and root activity were highest under 5 salinity, which were remarkably higher than other salinity treatments. The growth rate and biomass of B. sexangula var. rhynchopetala seedlings were all promoted under the treatment of low concentrations of salt, but all inhibited under the treatment of high concentrations of salt. The increment of the height, stem, and the number of the blade were highest when the salinity was 5, which were 10.8 times, 39.5 times and 19.6 times more than the minimum value when the seedlings were treated with 40 salinity respectively. The dry weight of leave, stem and root and the total biomass all increased first and then deceased with the increase of salinity. The dry weight of every organ of B. sexangula var. rhynchopetala seedlings were the most when the salinity was 5.The maximum of total biomass (5 salinity treatment) was about 25 times more than the minimum value (40 salinity treatment). The reaction of the underground part of B. sexangula var. rhynchopetala seedlings to salinity was more sensitive than the aboveground part. Analysis of principal component suggested the suitable salinity range for B. sexangula var. rhynchopetala seedlings are 0-25. The seedlings grew best under the 5 salinity treatment. While treating with >25 salinity, the growth of seedling was inhibited. This study provides a theoretical basis for the introduction, cultivation, genetic optimization and other further research of B. sexangula var. rhynchopetala.