Subthreshold micropulse laser(SML)consists of short repetitive pulses of laser. This kind of treatment is safe and cheap, and contrary to conventional laser photocoagulation(LPC), SML doesn't involve destruction of retinal cells and leave no scars. The possible mechanism of SML is to stimulate retinal pigment epithelium(RPE)cells for the production of heat shock proteins(HSPs)and regulate its metabolism and improve its function. The clinical indication of SML includes central serous chorioretinopathy(CSC), diabetic retinopathy edema(DME), nonproliferative diabetic retinopathy(NPDR)and proliferative diabetic retinopathy(PDR)and macular edema(ME)secondary to retinal vein occlusion(RVO). This article discussed the mechanism and safety of SML and reviewed the updates of its application.