Dry eye is a multifactorial disease characterized by loss of ocular surface homeostasis and increased tear film instability, accompanied by ocular symptoms such as ocular dryness, foreign body sensation, burning sensation, eye redness, pain, photophobia, tearing, eye fatigue, decreased visual acuity, increased secretion, and sensitivity to external stimuli. Its pathophysiological mechanisms are mainly tear film instability, elevated tear osmolarity(Tosm), ocular surface inflammation and injury, and neurosensory abnormalities. Tosm is an important factor in maintaining tear film stability and ocular surface comfort. Elevated Tosm can cause ocular discomfort, corneal epithelial damage, loss of goblet cells and ocular inflammatory response in dry eye patients, and the inflammatory response can further reduce tear film stability and increase Tosm, which puts dry eye in a vicious cycle. In order to have a more comprehensive understanding of the relationship between tear hyperosmolarity(THO)and dry eye, this article will focus on the role of THO in the pathogenesis, diagnosis, severity classification and targeted treatment of dry eyes from the aspect of pathophysiology.