To further improve the analysis methods of structural robustness, redundancy, and vulnerability, and to obtain the relationship between structural resistance and external load effect, optimization and reinforcement measures can be implemented for the weak or vulnerable parts of a structure to reduce the loss caused by damage or even safety accident due to the lack of structural resistance. Firstly, by reviewing the research progress of structural robustness, redundancy, and vulnerability and comparing different expressions of the current evaluation indexes, the essence of structural robustness, redundancy, and vulnerability were pointed out, and a new evaluation index based on strain energy was proposed. A further study on the relationship between structural robustness, redundancy, and vulnerability, as well as the basic influencing factors was also performed. Results have shown that structural robustness, redundancy, and vulnerability are from different fields and periods, which can reflect the resistance capacity of a structure, especially that of a damaged structure. The evaluation indexes are mostly subjectively defined by a complicated calculation process based on different levels of understanding. A widely accepted analysis method has not been established so far. Specifically, structural robustness and redundancy share similar evaluation index expression, both of which can represent the safety capacity or the remaining tolerance capacity of a structure. Structural vulnerability can directly reflect the structural failure extent, and it is inversely proportional to structural robustness and redundancy in the physical sense. Moreover, the increase in the material strength, the section size, and the structural restraint, together with the optimization of the load path, can increase structural robustness and redundancy and reduce structural vulnerability. The optimization and reinforcement measures can be implemented for the weak or vulnerable parts, thus structural damage, safety accident, as well as the loss cause by them, can be further reduced.