Probiotics have been considered a promising option for mitigating the progression of type 2 diabetes mellitus (T2DM). Here, QC9 ( QC9) with a hypoglycemic effect was screened out from 30 food-derived strains through α-glucosidase and α-amylase activity inhibition tests and a 4-week preliminary animal experiment. To further understand its alleviating effect on long-term hyperglycaemia occurring in T2DM, we conducted an experiment that lasted for 8 weeks. The results showed that taking QC9 can regulate glucose and lipid metabolism while improving the antioxidant capacity and alleviating chronic inflammation. In addition, our results demonstrated that QC9 may mediate the microbiota-gut-liver axis by regulating the composition of intestinal flora (increasing the abundance of butyrate-producing bacteria) and increasing the content of short-chain fatty acids (especially butyrate), affecting the PI3K/Akt signalling pathway in the liver, thereby achieving the purpose of alleviating the development of T2DM. In summary, our work is the first to prove the long-term hypoglycemic effect of in high-fat diet (HFD) and streptozotocin (STZ)-induced T2DM mice and supports the possibility of QC9 being used as a new treatment for alleviating T2DM.