AIM:To determine the agreement among Sirius pachymetric readings and the measurements made with Pentacam and ultrasonic pachymetry. METHODS:In this prospective study, 51 patients（102 eyes）with refractive surgery were enrolled and performed Pentacam and Sirius acquisitions followed by ultrasonic pachymetry. Pachymetric readings on central corneal thickness were recorded with Sirius, Pentacam and the ultrasonic system. Data were compared using t-tests, and the Pearson correlations and Bland-Altman analysis of all pairs were determined. RESULTS:Overall, ultrasonic measurements were significantly lower than all readings from the Sirius and the Pentacam，the Sirius was closest to the ultrasonic measurements values.In those Bland-Altman plots,3.92% of Sirius-Pentacam differences falled outside the 95% confidence limits for the mean difference.Within the limits of agreement,the maximum Sirius-Pentacam absolute difference was 19.5μm. 2.94% of Sirius-ultrasonic pachymetry differences falled outside the 95% confidence limits for the mean difference.Within the limits of agreement, the maximum Sirius-ultrasonic pachymetry absolute difference was 18.667μm. 5.82% of Pentacam-ultrasonic pachymetry differences falled outside the 95% confidence limits for the mean difference.Within the limits of agreement, the maximum Pentacam-ultrasonic pachymetry absolute difference was 25.33μm. CONCLUSION:Sirius system and Pentacam system have a good agreement , and the Sirius system is closer to ultrasound readings than Pentacam system over the results of corneal thickness.