Abstract: 【Objective】 The objectives of this study were to elucidate the structural characteristics and biological functions of the SlSIP gene from shrub Salix and to provide a theoretical basis for the new function of alkaline alpha-galactosidase gene. 【Method】 An alkaline α-galactosidase gene encoding SlSIP was cloned from the cDNA template of Salix jiangsuensis ‘2345’ after salt stress for 48 h. A bioinformatics method was used to analyze the protein structure and relationships. The expression level and function of SlSIP were conducted through agrobacterium-mediated transformation into Arabidopsis thaliana and real-time PCR. 【Result】 This gene encoded 776 amino acids with a molecular weight of 84.88 ku, a theoretical isoelectric point of 5.85, an unstable coefficient of 35.74, and the average hydrophilic coefficient of -0.154. It was located on the endoplasmic reticulum. The conserved domains of SlSIP were WFGWCTW and IDDGWQ with the catalytic active site V. In total, 11 positive T3 generation transgenic homozygotes were obtained. qRT-PCR showed that the expression level of SlSIP increased by 9, 28, 29 times in 3 Arabidopsis transgenic lines. The seed germination rate of the transgenic lines was higher than that of the wild type on 85 mmol/L NaCl medium, and the growth state was well, but the chlorophyll content of the wild-type plants was higher than that of the transgenic lines. 【Conclusion】 SlSIP belongs to the GH27 gene family. This indicated that the SlSIP gene not only increased the salt tolerance of seed germination, but also participated in leaf growth and senescence. This is the first study identifying the novel function of an alkaline α-galactosidase gene.