Objective To compare the adaptation of porcelain fused-to-metal（PFM） restorations made from Ni-Cr alloy, precious alloy and galvanized forming copings after cementation and to provide a theory guidance for their application. Methods Three kinds of crowns （Ni-Cr alloy, precious alloy and galvanized forming） were manufactured and cleaned by ultrasonic vibrate with alcoholic solution for 5 minutes, and cemented on their dies as their order. All the crowns were cemented by polycarboxylate zinc-cement and maintained 10 minutes. After coated in the center of methyl acrylic resins, all the samples were cut vertically along buccolingual direction. The cement thickness of PFM was measured by scanning electron microscope and the data were analyzed by multivariate ANOVA. Results No significant difference was found between the cement thickness of precious alloy crown and galvanized forming crown（P> 0.05）, while both of these two kinds of crown had significant differences in cement thickness with Ni-Cr crown（P
