Abstract: Thespesia populnea seedlings were treated with seven salt gradients including 5, 8, 11, 14, 17, 20, and 23 g·kg-1 in greenhouse. The increment, biomass, physiological indexes and photosynthetic rate of Thespesia populnea seedlings with different salinity treatments were determined, combined with the adaptability analysis of physiological indexes. The results showed that the height, stem, leaf, root dry weight, stem dry weight, leaf dry weight and total biomass decreased with increasing of the salt, and they kept high values when the treatment salt were 5 and 8 g·kg-1, but they decreased suddenly when the treatment salt were more than 11 g·kg-1. The photosynthesis of Thespesia populnea seedlings were high under the salt treatment of 5, 8 and 11 g·kg-1, and the maximum value was under the salt treatment of 8 g·kg-1.With the increasing of salinity, the SOD, free proline and MDA increased, but chlorophyll, chlorophyll A and root activity decreased. The adaptability analysis of physiological indicator showed that Thespesia populnea seedlings grew normally when the treatment salt was no more than 8 g·kg-1, and the growth would be inhibited when the salinity was more than 11 g·kg-1.