There was no significant difference in the parameters of biomechanics between normal group and forme frusta keratoconus group (P>0.05).Compared to normal group and subclinical keratoconus group,the parameters second applanation length(AL2),first velocity of applanation (AV1),central curvature radius at highest concavity (HC-radius),deformation amplitude (DA) were revealed statistically significant differences(P<0.05).The biomechanical parameters of the keratoconic group were significantly different from those of normal group except for the second velocity of applanation (AV2),time from the start until the highest concavity(HC-time),peak distance (PD).ROC curve showed that the DA(area under the curve0.891±0.028) was the best predictive parameter to distinguish keratoconus from the normal eyes.