The choroidal vasculature provides oxygen and nutrients to the outer retina, and is responsible for maintaining the highly metabolically active photoreceptor cells. The normal structure and function of its vascular system is very important for the retina. So it is more meaningful to observe the choroid morphology for tracking pathological changes in diabetic retinopathy. With the application of the high resolution optical coherence tomography(OCT)technology, spectral-domain optical coherence tomography(SD-OCT)enhanced depth imaging technology can be used to measure the choroidal thickness quantitatively, which provides a new idea for the diagnosis and treatment of diabetic retinopathy. Therefore, the research and progress of choroidal thickness on diabetic retinopathy by OCT are summarized as follows.