In this study, via the retinal functional imaging device, not only the structural information of the retina is imaged, but also the functional information such as the retinal oxygen saturation and vessel diameter is imaged and measured noninvasively and quantitatively. By comparing quantitatively the functional imaging results of diabetes patients and healthy controls, significantly elevated arterial oxygen saturation and arterial-venous oxygen saturation difference are found in diabetes patients. The area of the foveal avascular zone is also significantly increased in diabetes patients. The result also shows that there are significant differences between the average diameters of arteries and veins both in diabetes patients and healthy controls, and the arterial diameter is always larger than the venous diameter. The study demonstrates that by using the retinal functional imaging method, the clinical changes of retinal oxygen metabolism as well as the perfusion rate in diabetes patients can be detected, which helps doctors to better observe and evaluate the pathological changes of the retinal microvessels in diabetes patients. In addition, the retinal functional imaging technique has the application potential for the early diagnosis and prognostic evaluation of ophthalmic complications associated with diabetes.