To investigate the mechanism of the hypoglycemic effect of immature guava fruit extract on diabetic mice， a diabetes mouse model was established through streptozotocin induction. The mice were divided into normal， normal hypoglycemic， model， positive control， and high， medium， and low dose groups of immature guava fruit extract. The fasting blood glucose， glucose tolerance， and lipid profile of the mice were measured. Pathological observations were conducted on the liver， kidney， and pancreatic tissues， and a non-targeted metabolomics study was carried out on the serum samples to investigate the therapeutic effects of immature guava fruit on diabetic mice. The results showed that， compared to the model group， the high-dose immature guava fruit extract significantly reduced the blood glucose levels (P<0.05) and improved the glucose tolerance (P<0.05) in diabetic mice. It also lowered the levels of serum triglycerides and total cholesterol (P<0.05)， and exhibited a certain protective effect on the liver， kidney， and pancreatic tissues (tissue morphology integrity) of the diabetic mice. Through serum metabolomics analysis， 27 significantly altered differential metabolites had been screened out， and it had been clarified that cortisol synthesis and secretion were the most relevant metabolic pathways. Conclusion: The aqueous extract of immature guava fruit had exhibited certain effects in lowering blood glucose， regulating lipid levels， and protecting liver， kidney， and pancreatic tissues. It had achieved the improvement of diabetes by regulating the body's cortisol hormone levels.