Objective To compare corneal topography index measurements of normal and subclinical keratoconus eyes obtained with Pentacam and Orbscan-Ⅱ， providing evidence for seeking a sensitive index with the 2 instruments to identify subclinical keratoconus. Methods Thirty normal eyes from 30 participants and 22 subclinical keratoconus eyes from 22 participants were included for measurements with Pentacam and Orbscan-Ⅱ for a retrospective analysis. The differences between normal and subclinical keratoconus eyes were compared for the 7 common corneal topography indexes measured by Pentacam and Orbscan-Ⅱ. The measurements included corneal thickness of the thinnest point （TP）， the minimum curvature of the front surface （K1）， the maximum curvature of the front surface （K2）， the anterior corneal surface best fit spherical radius of curvature （ABFS）， the posterior surface of the cornea behind the best fit spherical radius of curvature （PBFS）， the anterior corneal surface height （front Diff value） and the posterior corneal surface height （posterior Diff value）. A rank sum test was used to compare the same parameters between Pentacam and Orbscan-Ⅱ （dates were non-normally distributed）. The test was also used to compare two related samples obtained by the 2 instruments （dates were non-normally distributed）. Results The 7 common parameters measured with Pentacam and Orbscan-Ⅱ showed obvious differences between the normal and subclinical groups. Thus， the 7 parameters have significance in the diagnosis of keratoconus. There were significant differences between Pentacam and Orbscan-Ⅱ in the topography indexes for the normal group （P<0.01） for K1， front Diff value （P<0.01）， and posterior Diff value （P<0.01）. For the subclinical group， there were statistically significant differences （P<0.01） for TP， front Diff value （P<0.01） and posterior Diff value （P<0.01）. Conclusion TP， K1， K2， ABFS， PBFS， front Diff value and posterior Diff value are closely related to the development of keratoconus. Pentacam has an advantage compared to Orbscan-Ⅱ in the measurement of indexes for the surface height， except for the posterior surface.