Diabetic macular edema(DME)is a major cause of visual impairment in patients with diabetes mellitus, the central retinal thickness(CRT)is correlated with the visual impairment and the changes of visual function before and after treatment. Furthermore, CRT is related to the changes of macular microstructure. The subtle changes of retinal microstructure can be qualitative and quantitative analyzed by spectral-domain OCT(SD-OCT). In this study, the changes of retinal microstructure in patients with DME are reviewed, what is of great meaning to explore mechanism, observe disease progress, guide clinical treatment and prospect prognosis of DME.