Aim To study the protective effect of growth hormone releasing hormone receptor agonist MR409 on vascular calcification (VC) in gene deficient mice Db/Db diabetic mice (Db/Db mice). Methods With 12-week-old male wild-type (WT) C57BL/6 mice as the WT group (control group), 12-week-old male Db/Db mice were randomly divided into Db/Db group (diabetes group) and MR409 group (MR409 treatment group). MR409 group was given MR409 (15 μg/time) every other day for 8 weeks. At the end of the 8th week, the mouse serum alkaline phosphatase (ALP) and blood glucose levels were tested. HE staining was used to observe the morphological changes of aorta in mice. Calcium salt deposition in aorta was detected by von Kossa staining and alizarin red staining. Endothelium-dependent vasodilation function was measured by in vitro vascular perfusion system. Aortic calcification-related protein Runt-related transcription factor 2 (Runx2) protein expression was detected by immunohistochemical staining. Aortic reactive oxygen species (ROS) level was detected by dihydroethidium fluorescent staining. Results Compared with WT group, serum ALP activity increased, blood vessel wall thickness increased, vasodilation function decreased, and aortic ROS level increased in Db/Db group (P＜0.05). Compared with Db/Db group, ALP activity decreased, aortic hypertrophy decreased, vasodilation function improved, and ROS level of aorta decreased in MR409 group (P＜0.05). Compared with WT group, there was significant VC in Db/Db group, which showed increased calcium salt deposition and increased Runx2 protein expression in aorta (P＜0.05). Compared with Db/Db group, calcium salt deposition and Runx2 protein expression in aorta were decreased in MR409 group (P＜0.05). Conclusion MR409 can significantly inhibit VC, reduce aortic hypertrophy and improve vascular endothelial function in diabetic mice, and its mechanism may be related to the inhibition of the increase of Runx2 expression induced by oxidative stress.