Abstract: Structural robustness requires that the structure is capable of resisting disproportionate collapse. How to evaluate the structural robustness quantitatively is one of the most challenging problems in structural engineering. From the structural bearing capacity, the paper proposes a new method to calculate the importance coefficients of components. And then according to the importance coefficient, a new indicator of structural robustness and a new method to evaluate it are presented. Therefore, the quantization of structural robustness has been realized. The method for quantizing structural robustness is illustrated in examples which use plane truss structures and plane frame structures. The computation result implies that the ranking of the robustness indicators of 4 plane frame structures which have the same width and height is consistent with the result of the qualitative analysis, showing the rationality of the proposed robustness indicator. At last, through comparing and analyzing the robustness indicators of the 4 frame structures, some factors that affect the structural robustness are obtained, including load type, span uniformity, total span number and brace.