AIM:To investigate the effect of different stage of primary hypertension on corneal endothelial cells by Specular Microscope. METHODS:Case-control study was taken. The case group included 71 patients(142 eyes)diagnosed with primary hypertension, including 22 patients(44 eyes)in group stage 1, 23 patients(46 eyes)in group stage 2 and 26 patients(52 eyes)in group stage 3. The control group included 69 healthy subjects(138 eyes). There was no statistical differences in gender and age(P>0.05), and no systemic or eye disease for the both groups.Statistical analysis was made on the corneal endothelial cells including average cell area, average cell density, coefficient of variation and percentage of hexagonal cells. RESULTS:Average cell area and average cell density had no statistical differences for both groups. Coefficient of variation increased(t=3.34, Pt=-2.07, PP>0.05). There was significant differences for coefficient of variation and percentage of hexagonal cells(P CONCLUSION:Compared with the control group, corneal endothelial cells of patients with primary hypertension increases significantly on coefficient of variation and decreases on percentage of hexagonal cells. Patients with different hypertension grades have different coefficient of variation and percentage of hexagonal cells.