Abstract: Preclinical diabetic retinopathy refers to the stage of disease in which the function of retina has declined but visible fundus lesion is not found. This paper reviewed the research progress of preclinical diabetic retinopathy in recent years by comparing the clinical parameters, pathological changes and some systemic indexes of ophthalmology, and summarized the correlation among the three, which is helpful for the diagnosis and progress monitoring of preclinical diabetic retinopathy.