AIM:To detect the incidence and mechanism of high intraocular pressure(IOP) at the early stage after small incision non-phacoemulsification cataract surgery. METHODS:Totally 116 patients (116 eyes) who had undergone small incision non-phacoemulsification cataract surgery in our hospital in the first half of 2011 were retrospectively analysed. RESULTS:Among the 116 eyes，postoperative IOP elevation occurred in 35 eyes (about 30.2%).The IOP reached the peak mostly 6 to 24 hours after the surgery, up to 56mmHg (1mmHg = 0.133kPa). 88.6% of high IOP occurred at the same time. And in this period the incidence of IOP elevation were significantly higher than in other periods (P<0.01). 62.9% of high IOP rose slightly, less than 30mmHg. CONCLUSION:The incidence of higy IOP at the early stage after small incision non-phacoemulsification cataract surgery is high, but most of the IOP rose slightly. The most common reason is that some substances blocked the trabecular meshwork. These substances were residual viscoelastic agent, residual cortex, denatured red blood cells, macrophages and pigment particle.These substances blocked the trabecular meshwork, and aqueous humor outflow was obstructed, and then the IOP rose. Other reasons also included IOL subluxation, endophthalmitis, etc.