A strain of Lactobacillus was successfully isolated from fermented goat milk and identified as Lactiplantibacillus plantarum 1-9, which could efficiently utilize stachyose as the carbon source. In order to investigate the mechanism for stachyose metabolization by Lactiplantibacillus plantarum 1-9, the growth curve was established with stachyose as the only carbon source. The production of short chain fatty acids was monitored by high performance liquid chromatography, while thin-layer chromatography were used to monitor the metabolic procedures of stachyose by Lactiplantibacillus plantarum 1-9. Besides, on the basis of monitoring the gene expression of key stachyose metabolizing enzyme, the changes of related enzyme activity in fermentation broth were analyzed. The results showed that Lactiplantibacillus plantarum 1-9 metabolized stachyose and produced acetic acid and valeric acid as the major short chain fatty acids, which reached the highest concentration of 28.64mg/mL and 2.74mg/mL, respectively. The accumulation of short-chain fatty acids resulted in a significant decrease of pH to 4.00. Based on the results of metabolic procedure of stachyose and changes of gene expression and enzyme activity, gene 5-359 in the genome of Lactiplantibacillus plantarum 1-9 might encode α-galactosidase. This segment could hydrolyze the α-galactoside bond at the end of stachyose and produce galactose and small amount of lactose and sucrose, thus facilitating the utilization of stachyose by Lactiplantibacillus plantarum 1-9. This study aimed to provide theoretical reference for the reasonable design of symbiotics based on Lactiplantibacillus plantarum and stachyose, and the development of related products.