Electroretinogram(ERG)is an objective examination in evaluating retinal function, which is also suitable to evaluate retinal function of multiple ophthalmic diseases. In recent years, studies have found that ERG can find functional changes prior to morphological changes of fundus examination in early diabetics, which provides a new way for researches of pathological mechanism, early diagnosis and prognosis evaluation for diabetic retinopathy, and then also provides a new therapy for diabetic retinopathy. In this paper, using ERG in the diagnosis of early diabetic retinopathy was reviewed.