Diabetic retinopathy(DR) is the most common diabetic eye disease and a leading cause of blindness in adults.It is caused by changes in the blood vessels of the retina.In some people with DR,blood vessels may swell and leak fluid.In other people,abnormal new blood vessels grow on the surface of the retina.The retina is the light-sensitive tissue at the back of the eye.A healthy retina is necessary for good vision.The following are very important for preventing DR and several procedures or laser eye surgery or vitrectomy are the main treatments.To truly recognize and understand the DR classification and international clinical DR severity scale helps to treat,and can catch problems early.There are many ways to make DR classification and severity scale.This paper is summarized and compared with some famous international institutions for DR clinical research content and conclusion.