To investigate the clinical use of glass ceramic onlay in the restoration of the non-vital posterior teeth with computer aided design and computer-aided manufacturing technique（CAD/CAM）.

70 patients with 75 teeth of residual crown were selected and restored with CAD/CAM glass-ceramic onlay after completely root canal therapy. Marginal adaptation, anatomic form, adjacent relation, contour appearance, color match were checked in 12-month follow-up.

Marginal adaptation, anatomic form, adjacent relation, contour appearance, color match of 73 teeth were satisfactory and 2 cases was excluded because of lost to follow-up. There were no significant differences in the number of cases which met clinical criterion A or B between immediate restoration and 12-month follow-up（P＞0.05）, and more than 95% of cases met clinical criterion A.

The CAD/CAM glass-ceramic onlay in the restoration of non-vital posterior teeth can provide better effect of retention and esthetics in a short term observation of 12 months.