A gene family called Strictosidine synthase like (SSL) exists in Arabidopsis thaliana genome.  Orthologs gene in Catharanthus roseus is involved in monoterpenoid indole alkaloids biosynthesis. A member of gene family (SSL6) has been induced by various biotic and abiotic stresses. To further analyse of the functional role of the gene in response to salt stress, the SSL6 T-DNA insertional mutant (ssl6) was used in response to 0, 100 and 200 mM NaCl. Therefore, several morphological, physiological and molecular traits including the percentage of seed germination, root length, Catalase (CAT), Peroxidase (POD) and Superoxide dismutase (SOD) enzyme activity, and relative expression levels of AAO3, RD29A, NCEDD3 and P5CS1 were measured. The obtained data have been analyzed using a factorial experiment (with two factors) based on completely randomized design (CRD) with three replications.  The obtained results demonstrated that the percentage of germination, root length and activity of SOD, POD and CAT enzymes were significantly higher in ssl6 genotype when compared with the wild type Col-0. The expression level of responsive genes at 3 and 6 h after salt stress treatment were significantly increased in ssl6 mutant genotype compared to Col-0 genotype. Results of this study for the first time reported that SSL6 genes in involved in plant responses to salinity stress and suppression of SSL6 gene resulted in increased tolerance to salt stress in Arabidopsis.