Diabetic fundus hemorrhage, is the occurrence of diabetic retinopathy, and retinopathy requires laser treatment, which requires understanding the mechanism of laser treatment for diabetic retinopathy. So what is the mechanism of laser treatment for diabetic retinopathy? There are two main mechanisms: one is localized laser photocoagulation to close the leaks of blood vessels or microangiomas in the retina. The other is the use of large area photocoagulation, which destroys the photoreceptor cells of the outer retina and the retinal pigment epithelium, which consume the most oxygen, and reduces the oxygen demand of the retina and decreases the metabolic level. The thinning of the retina allows the oxygen from the choroid that would have been supplied to the outer retina to diffuse to the inner retina, raising the partial pressure of oxygen in the inner retina and thus relieving retinal hypoxia. In conclusion, after extensive retinal photocoagulation, retinal blood flow decreases, dilated vessels contract, autoregulation improves, small arteries also contract, intravascular and transmural pressures in capillaries and small veins are reduced, vascular leakage decreases, and thus retinal edema is reduced, tissue hypoxia is relieved, and neovascularization degenerates.