Raffinose family oligosaccharides（RFOs）are one of important osmoregulatory substance in plants. Galactinol synthase（GolS）is a key enzyme in the synthesis of RFOs. In this study，GmGolS1 was cloned from soybean based on sequence homology. GmGolS1 was found on chromosome 3 with three introns. The full length open reading frame（ORF）of GmGolS1 was 1020 bp，which encodes 339 amino acids with the molecular weight of 38.82 kDa，and the isoelectric point of 5.47. The amino acid sequence GmGolS1 has characteristics that are commonly detected in plant GolS proteins：a conserved serine phosphorylation site，a manganese ion binding associated DXD element，and a carboxy-terminal hydrophobic pentapeptide. The phylogenetic analysis showed that GmGolS1 was closely related to AmGolS and MtGolS. Real-time fluorescence quantitative PCR analysis showed that GmGolS1 was inducible upon heat，low temperature，drought and salt stresses in different degrees in seedlings，and the most abundant expression was observed under heat stress treatment. By transforming GmGolS1 was into tobacco，four transgenic lines were identified using genomic DNA PCR and real-time fluorescence quantitative PCR. Test for GolS enzyme activity showed that the transcribed product of GmGolS1 in transgenic tobacco played the catalytic activity of GolS. Gained from plant phenotype，electrolyte leakage，soluble carbohydrate content and malondialdehyde content of GmGolS1 transgenic tobacco under heat stress，GmGolS1 was found correlating with improved heat resistance in transgenic tobacco.