S-Adenosylmethionine (SAM) synthetase catalyzes the synthesis of SAM, a vital molecule nearly existing in all cellular organisms.It is also considered to play an important role in salt tolerance of plants.Here, we cloned a Lycoris radiata (L.radiata) SAM synthetase gene LrSAMS to determine its biological function.The cDNA contains a 1206 nt of continuous complete open reading frame (ORF) encoding a polypeptide of 401 amino acids with a calculated molecular mass of 43.9 kDa.Sequence comparison of the deduced protein LrSAMS reveals high amino acid sequence identity with SAM synthetase from other organism, such as Arabidopsis thaliana and Oryza sativa.The deduced LrSAMS protein contains conserved amino acids residue and sequences motifs closely related to function of SAM synthetase.Otherwise, the transcript levels of LrSAMS were significantly induced by NaCl treatment in Lradiata leaves, which implied that LrSAMS may play an important role in tolerance to salt stress in L.radiata.Complete ORF of LrSAMS was inserted into expression vector pET-29a (+) and transformed into Escherichia coli BL21 (DE3).The difference between the growth curve of the transgenic strain and control strain with blank vector showed that over-expressing LrSAMS could provide growth advantage to the engineered strain in high salt concentration.