Incidence rate of diabetes mellitus(DM)rises up obviously around the world. This disease can cause diabetic retinopathy, diabetic keratopathy, cataract, glaucoma, refractive changes, iridociliary disorder, dry eyes and other ophthalmic complications, which severely affect vision and even result in blindness. In recent years, with improvement of life quality, it is gradually frequent for diabetics to see ophthalmologist on account of sore eyes. This phenomenon has attracted attention of oculists, which is related to abnormal factors such as abnormal tear quality and quantity under diabetes condition, poor stability of tear film, rising of tear osmotic pressure, inflammatory response, cornea neurodegeneration, apoptosis, functional lesion of tarsus related to sex hormone. As over 90% of diabetics are diagnosed as type 2 diabetes mellitus(T2DM), this paper will summarize pathogenesis of dry eyes related to T2DM and offer theoretical foundation to clinical diagnosis and treatment.