To evaluate the effect of cement gap and drill offset on the marginal and internal fit discrepancies of crowns designed with different tooth preparations. Five tooth preparations were constructed, and crowns with different cement gaps and drill offset were obtained. Then, best-fit-alignment was performed on the crowns with the corresponding tooth preparations, and the fit discrepancies were expressed by the color-code difference images and root mean square (RMS) values. The RMS values of each group were analyzed by the rank-based Scheirer-Ray-Hare test (α=0.05). The color segments in the sharp line angles area of the Sharp line angles group changed significantly before and after the drill offset. The cement gap had a significant effect on the marginal, internal, or overall fit discrepancies of the five design groups (P<0.001), while the drill offset had a significant effect on the marginal fit discrepancies of the Shoulder-lip group and the internal or overall fit discrepancies of the Sharp line angles group (P<0.001). Additionally, the interaction effect between cement gap and drill offset was significant for the marginal fit discrepancies of the Shoulder-lip group and the internal or overall fit discrepancies of the Sharp line angles group (P<0.01). The cement gap and drill offset had a significant adverse effect on the marginal or internal fit discrepancies in the crowns designed with the shoulder-lip and sharp line angles designs. Designs of tooth preparation with intense curvature changes such as shoulder-lip and sharp line angles should be avoided clinically.