Elevation of intraocular pressure (IOP) is a major risk factor for the development and the progression in glaucoma optic nerve damage. The reduction of IOP remains mainstream strategy of glaucoma therapy. A large fluctuation of IOP in the circadian rhythm may play a role in the optic nerve damage in glaucoma progression. IOP monitoring provides important information of IOP mean, peak and fluctuation to assist the diagnosis and treatment of glaucoma. With the development of technology, the commonly used methods of IOP monitoring including IOP measurement for diurnal, 24 hours, and habitual body position have evolved to continuous IOP-monitoring using novel device. The influencing factors including tonometer, body position and the light have been taken into account for the reliability of IOP measurement. In this review, we summarized the recent progress in IOP monitoring and the factors affecting the IOP measurements and discussed immense opportunity of IOP-monitoring to better diagnose and to treat for glaucoma.