This paper expounded the importance of reliability study on low-voltage circuit-breakers and residual current operated circuit-breakers, introduced the general situation of their reliability study carried out by the international authoritative academic academy IEEE and pointed out the difficulty and significance of the research work on these aspects. Then this paper discussed the failure modes of low-voltage circuit-breakers and residual current operated circuit-breakers, and provided their reliability indexes and reliability compliance test plans at the first time, which provided a kind of theory and method for the reliability research work of low-voltage protective electrical apparatus carried through in Chinese electrical apparatus industry.