Abstract： Objective To analyze the discipline of intraocular pressure (IOP) variation, through circadian intraocular pressure monitoring in primary open-angle glaucoma (POAG) patients and normal controls, with a view to provide basis for individualized treatment of glaucoma. Methods Subjects were enrolled from the outpatients of Shanghai Beizhan Hospital and Eye and ENT Hospital of Fudan University,which were diagnosed as primary open angle glaucoma, from April 2006 to April 2009. Totally there were 102 cases of patients and 83 cases of normal volunteers. All the subjects accepted 24-hour IOP measurements using non-contact tonometer every two hours starting from 8:00 am. And the IOP between O0:00 to 06:00 am was measured in sitting position immediately after wake up. Results The differences of peak IOP[ (16.0±2.7)mm Hg of right eye and ( 16.2±2.7)mm Hg of left eye in normal group; (25.3±5.6) mm Hg of right eye and (24.8±5.1) mm Hg of left eye in POAG group], valley IOP ( 11.1±2.5) mm Hg of right eye and (11.0±2.3) mm Hg of left eye in normal group; ( 16. 3 ±3.7) mm Hg of right eye and ( 16.2 ±3. 3 ) mm Hg of left eye in POAG group, average IOP (13.4±2.5) mm Hg of right eye and ( 13.4 ± 2.5)mm Hg of left eye in normal group; ( 19.9 ±4.3) mm Hg of right eye and ( 19. 8 ±3. 8) mm Hg of left eye in POAG group), and IOP fluctuations (5.0 ± 1.6) mm Hg of right eye and (5. 2 ± 1.7) mm Hg of left eye in normal group; (9.1 ±3.6) mm Hg of right eye and (8.6±3.8 ) mm Hg of left eye in POAG group between two groups were all of statistically significance (P ＜ 0. 01 ). Notably, the peak IOP of 59. 6% in normal control group and 73.5% in POAG group were outside working hours, especially in the time period from 00:00 to 06:00 am. The peak value of 50% in normal group and 64.7% in POAG group located between 00:00 to 06:00 in the morning. Conclusions By comparison and analysis, 24-hour intraocular pressure measurement could provide us pre-treatment basic state, so as to provide detailed information for individualized treatment. If possible, it is suggested that 24-hour IOP monitoring should be added as a routine examination of primary open angle glaucoma.