Objective: To evaluate the clinical significance of self-monitoring 24-hour intraocular pressure (IOP) in  primary open angle glaucoma (POAG) patients with medical treatment. Methods: This was a case series  study. Forty-two POAG patients who had acceptable clinic IOP reading controlled by medicine were  selected in shenyang Aier Eye Hospital from August 2017 to January 2019, and divided into group A (IOP:  12.86±1.40 mmHg) and group B (IOP: 17.82±1.40 mmHg) based on the baseline IOP. All participants  were trained to use the iCare HOME rebound tonometer to measure 24-hour IOP at home by themselves  after certification. 24-hour IOP values was obtained every 2 hour starting from 7:30. The IOP was measured immediately in sitting position after waking up during 23:30 to 5:30. The observation indices included mean  IOP, peak IOP and IOP fluctuation amplitude in different periods. The timing of peak IOP and the proportion  of patients changing treatment were counted. One-way ANOVA, Kruskal-Wallis H test, t-tests and χ2  test were  used to analyze the data. Results: There was no significant difference among the mean IOP measured in the  period of clinic, office hours and 24-hour (F=1.314, P=0.271). The peak IOP during 24-hour was higher than  that during office hours and that during the clinic period (H=-40.979, -51.363, all P<0.001). 83.6% of the  patients' peak IOP occurred outside the office hours (86.5% in group A and 80.6% in group B), especially in  the night, with a proportion as high as 67.1% (64.9% in group A and 69.4% in group B). The 24-hour IOP  fluctuation of all patients, as well as the patients in group A and group B, were higher than that during office  hours (t=11.166, 8.110, 7.929, all P<0.001). 63.0% patients' 24-hour IOP fluctuation was greater than or equal  to 8 mmHg (51.4% in group A, 75.0% in group B). 49.3% patients' clinical management was changed based on  the result of self-monitoring 24-hour IOP, and the changing proportion in group B (63.9%) was higher than that  in group A (35.1%) (χ2 =6.035, P=0.014). Conclusions: Self-measurement of 24-hour IOP in POAG patients  with medical treatment would identify IOP peaks and fluctuations missed in routine clinical practice, which can  be used as an important evidence for clinician to evaluate therapeutic effects and adjust clinical management.