Objective To investigate the application of optical impression and model scanning after silicone rubber impression in full crowns adaption by Computer Aided Design and Computer Aided Manufacturing (CADCAM). Methods Ceramic full crown was prepared for Mandibular left first molar (Nissin Dental Products, Japan). Impressions were made by optical scanning (group A) or silicone rubber (group B) (n = 10). The adaption of crowns was measured by silicone replica technique and inverted phase contrast microscope (Olympus BX43). All data was processed using SPSS 20.0 for statistical analysis. Results Marginal adaptation (μm) in group A and group B was (44.38 ± 9.64) and (42.39 ± 13.02) (P = 0.817), respectively. Occlusal adaptation (μm) was (80.26 ± 31.71) and (75.25 ± 6.07) (P = 0.729), respectively. No significant difference was founded between two groups in terms of cement thickness (P > 0.05). Cement space among different measurement sites in group A was similar, while cement space at the same measurement site in group B was more centralized. Conclusion Two methods are comparable in marginal adaptation and internal adaptation, both of which are clinically acceptable.