The physical mechanisms between residual strength and crack characteristic of ceramics after water‐quenching are studied by statistically measuring the cracks in ceramic sheet. The result herein reveals that in the joint action of long crack length and density, the residual strength is maintained at the same level within a temperature range above the critical thermal shock temperature difference (ΔTC). The result presented herein forms a further comprehension to the ceramics behaviors of and the theoretical approaches to thermal shock.