Flaws in ceramics have a significant impact on their strength. Realization of ceramic strength from qualitative statistical description to quantitative prediction is essential for the fields of fracture mechanics, materials science and engineering applications. In this study, two regular flaw-strength prediction models with clear physical meaning were established under I-mode failure according to the classic crack-strength model (Sato [17]) combined with two critical stress intensity factor Kc vs. tip radius r relationships (Gómez [18] and Yang [19]). Comparison with the data that reported in the literature proved that the Sato-Yang model was more accurate than the Sato-Gómez model. On the basis of finite element simulation and mathematical fitting, a simple coefficient that can reasonably described the complexity of flaw shapes was proposed, thus extending the regular flaw-strength model to solve the irregular flaw problem and passing the experimental verification at the same time.