Diagnosis of early keratoconus(KC)contributes to identifying potential patients before typical clinical symptoms. It also contributes to timely intervention of the progress of disease and improvement of long-term prognosis. Hence, it is crucial to prevent iatrogenic corneal ectasia and reduce the burden of keratoplasty. There are diverse kinds of early KC diagnosis techniques, including corneal topography, corneal aberrations, epithelial and corneal thickness measurement, corneal confocal microscopy, corneal biomechanics, and genetic examination. Since it is often difficult to ensure sufficient sensitivity and specificity with single technique, multiple techniques are beneficial to evaluate the cornea comprehensively, which may become the development tendency of early KC diagnosis in the future.