Abstract: Background The coastal saline soil is formed by the seawater immersion in the river sediments, with salting and salt characteristics of a typical modern seawater effects. The typical characteristic of coastal saline-alkali soil is that the content of NaCl and the groundwater level are high.Chlorides, sulfates and salt content in the soil directly affect the survival of the germination of seeds, limiting the growth and yield of plants, which has become the most direct factor of vegetation restoration in coastal saline-alkali soil area. Ulmus pumila L. is the most widely distributed and important fast growing hardwood timber species that has solid tolerance to drought, cold, salt and wind. It is the most important timber species in vast north plains, salinealkali areas and desert to construct useful afforestation, shelter forest and greenings. Methods In order to cultivate, modify and utilize salinized soil of coastal saline area, 3 elm clones (Y65225, Y46 and Y51) were chosen as test materials, watering with 5 salt concentrations of 0.0%, 0.3%, 0.5%, 0.7%, and 0.9% by pot-cultivated experiments in the greenhouse. The activities of dismutase (SOD), catalase (CAT), peroxidase (POD) and mass content of malondialdehyde (MDA) were determined in this study. The change of antioxidant enzymes activity and mass content of MDA and the correlation of the indexes were analyzed. In addition, salt resistance of the 3 clones was comprehensively evaluated by subordination function method. Results Y51 sustained high antioxidant enzyme activity under different salt concentrations, meaning it had the strongest antioxidant capacity. While as the antioxidant capacity of Y46 was the worst, because its antioxidant enzyme activity decreased in greatest. MDA was an important indicator of injured cell membrane, which shows that the seedlings are efficiently influenced by the membrane lipid peroxidation. The activities of MDA increased with the salt stress increasing, the greatest increase was from Y46, while the smallest from Y51 and the salt injury to Y51 was the least. The correlation analysis of the measurement indicators for 3 elm clones showed that the correlation of SOD activity and POD activity were significant; besides the CAT activity presented no significant correlation with the above two indicators. The activities of CAT and POD had little significance with the mass content of MDA. Moreover, the activity of SOD showed certain negative correlation with the mass content of MDA, i. e., the increase of SOD significantly reduced the accumulation of MDA mass content, and therefore enhanced the salt resistance of the elm clones. Conclusions Ultimately, through overall assessment, salt resistance of Y51 was the highest, less for Y65225 and the lowest for Y46, indicating that they belonged to the middling salt-tolerant elm clones. We recommend that Y51 is the preferred clone in afforestation in the coastal areas. The results of this paper may also provide a certain theoretical significance for cultivating elm clones in the future.