Abstract: Salt stress severely affects the plant growth and development, and frequently leads to decreased crop yield. GIGANTEA（GI） is a plant specific protein that not only regulates the physiological processes such as photoperiod, flowering time, sucrose signal transduction, and starch accumulation, but also plays a role in drought, cold, and salt tolerance. However, the detailed study on the stress tolerant function of the GI protein in Jatropha curcas is lacking. The aim of this study was to investigate the role of JcGI, a gene in J. curcas, in regulating salt stress. In this study, bioinformatical analysis of J. curcas JcGI was conducted, and a JcGI gene overexpression vector was constructed. Transgenic Arabidopsis thaliana plants overexpressing JcGI were obtained through Agrobacterium tumefaciens-mediated floral-dip transformation. The wild type WT, gi mutant, and transgenic Arabidopsis thaliana lines with overexpression of JcGI were used to investigate the role of JcGI in regulating salt tolerance. The results showed that:（1）JcGI overexpressing lines exhibited a more pronounced inhibition of seed germination and root growth, and a significant decrease in chlorophyll content compared to the wild type and gi mutants under salt stress;（2） JcGI overexpressing lines showed increased levels of reactive oxygen species and hydrogen peroxide, and decreased levels of soluble sugars and hydrogen peroxide enzyme activity, while the opposite was observed in gi mutants under salt stress, meanwhile, the fresh weight, dry weight and survival rate of JcGI overexpressing lines was significantly lower than that of gi mutants;（3） Root growth of JcGI overexpressing lines was significantly inhibited, in comparison with that of gi mutants and wild type in the ABA medium, it also showed that the response of overexpression lines to salt stress and ABA was higher than that of gi mutants and wild types. These results suggest that JcGI overexpressing lines are more salt-sensitive, while gi mutants have higher salt tolerance. Overall, the results demonstrate that overexpression of JcGI negatively regulates salt tolerance in A. thaliana.