Objective To investigate the effect of carteolol hydrochlorideeye drops on 24-hour variation of intraocular pressure (IOP). Methods The 30 patientswho had never used any anti-glaucomaeye drops were chosen, and their 24-hour variation of IOP (at 200 AM, 600 AM, 1000 AM, 200 PM, 600 PM, 1000 PM) were measured. Then carteolol hydrochlorideeye drops were used twice a day (700 AM and 700 PM), 1-2 drops each time. Fifteen days later, their 24-h IOP was measured again and the data were analyzed. Results The average IOP at six monitoring points before treatment were (19.77±2.51) mm Hg, (19.52±2.34) mm Hg, (20.38±2.71) mm Hg, (20.07±3.65) mm Hg, (19.97±4.10) mm Hg and (19.97±4.31) mm Hg, the corresponding data after 15 days of treatment were (17.12±2.38) mm Hg, (17.42±2.60) mm Hg, (18.18±2.36) mm Hg, (18.02±3.77) mm Hg, (17.72±3.17) mm Hg and (17.35±3.40) mm Hg (t=11.68, P=0.000). The difference before and after treatment was (2.46±2.05) mm Hg during day and (2.17±1.88) mm Hg during night, and no significant difference was found between them. Conclusions Carteolol hydrochlorideeye drops could significantly reduce the IOP, the decreased extent of 24-h IOP is stable.