[Objective] The mechanism of Helianthus tuberosus in the improvement of coastal saline soil was explored, the compositional differences of root exudates of Helianthus tuberosus and Suaeda salsa was analyzed, and the changing laws of the soil micro-ecological environment were clarified, in order to provide a theoretical basis for saline soil improvement.[Methods] The root exudates of Helianthus tuberosus and Suaeda salsa were compared and analyzed, and the changes of soil microbial quantity, microbial biomass carbon and nitrogen, microbial community structure and soil enzyme activity under the action of root exudates were studied, so as to systematically clarify the microbial mechanism of saline soil improvement mediated by root exudates.[Results] The rhizosphere soil of Helianthus tuberosus contained fructose (2.343×10^-3 g/kg), glucose (4.235×10^-3 g/kg), and sucrose (2.67×10^-3 g/kg), which were 9.28, 1.52, 2.43 times of that in Suaeda salsa rhizosphere soil. The difference between the content of fructose in the rhizosphere and non-rhizosphere of Helianthus tuberosus was significant (p<0.05), and the content in the rhizosphere was 12.02 times of that in the non-rhizosphere. Helianthus tuberosus soil also contained oligofructose (sucrose triose, sucrose tetraose and sucrose pentaose), but no fructooligosaccharides were detected in the soil of Suaeda salsa. In addition to sugars, Helianthus tuberosus root exudates also contained alkanes, phenols, aldehydes, esters, organic acids, alcohols, ketones, and amides. Its components were more complex than Suaeda salsa soil and some components were unique to Helianthus tuberosus[1-Chloro-octadecane, n-hexadecanoic acid, 2-methyl-Z-4-tetradecene, dodecone, (Z)-9-octadecyl amide, and hexadecyl phenylpropionate Esters.] . Functional root exudates (such as oligofructose, fructose, hexadecane, and octadecanoic acid.) provided carbon source, nitrogen source and nutrient elements for rhizosphere microorganisms. The number of microorganisms in the rhizosphere soil of Helianthus tuberosus increased significantly (p<0.05), and the soil microbial biomass carbon and nitrogen were significantly higher than that in Suaeda salsa soil (p<0.05), which were 1.95 and 1.6 times of that in Suaeda salsa soil, and the microbial biomass carbon and nitrogen of Jerusalem artichoke rhizosphere were about 1.69 times and 1.50 times higher than that in non-rhizosphere soil. And the dominant flora (Proteobacteria, Actinomycota, Chloroflexum, Acidobacteria) accounted for 90%. The relative abundance of soil beneficial bacteria (Actinobacteria and Acidobacteria) increased significantly, and soil biological activity was significantly improved. In addition, the unique secretions of Helianthus tuberosus rhizosphere (hexadecane, and enal.) inhibited the growth of pathogenic bacteria and optimized the microbial community structure. Except for catalase, the activities of soil urease, invertase and alkaline phosphate were significantly increased (p<0.05), and their activities were 1.83 times, 1.88 times and 3.30 times higher than those in Suaeda salsa soil, respectively.[Conclusion] After planting Jerusalem artichoke, through the mediation of rhizosphere exudates, the structure and function of soil microbial community were improved, soil enzyme activity was increased, and soil biological activity was improved as a whole. Compared with the native vegetation Suaeda salsa, it reduces the salt content of the soil and plays a role in improving saline soil.