Diabetic retinopathy(DR), one of the most common complications of diabetes mellitus, is the leading cause of blindness in working-age population. DR, previously regarded as a microvascular disease, is also considered as neuronopathy and low-to-moderate inflammation in retina with research progression. Microglias, the resident macrophage in the inner retina, are responsible for surveillance of the microenvironment in retina. Under abnormal conditions, microglias are activated and interact with different types of cells in retina. In DR, microglias become activated, as evidenced by the activation of the key molecules or signal transduction pathways, such as the nuclear factor kappa-light-chain-enhancer of activated B cells(NF-κB)and extracellular signal-regulated kinase(ERK)signaling pathways, which lead to the increased production of pro-inflammatory factors, chemokines, etc. At the same time, the proliferation and migration of activated microglia are enhanced, and microglias migrate to the outer retina. The over-activation of microglias causes neuronal cell apoptosis and blood-retinal barrier breakdown, resulting in vision loss.