This paper is devoted to a critical analysis of two types of moral responsibility ascription theory which are contrary to each other and have respectively been proposed by Harry Frankfurt, John Martin Fischer and Mark Ravizza. Both of Frankfurt's theory typically represented in “Alternate Possibility and Moral Responsibility”’ and Fischer's theory typically represented in “Responsibility and Inevitability” has its own weakness at the same time with strength. Whereas Fischer's theory has reasonably pointed out the weakness of Frankfurt' theory, his views on the requirements for the “omission” to be morally responsible is some of narrow-minded and would in some circumstances be morally indulgent with omission. The key cause that leads such a weakness to Fischer's theory consists in two factors: One is that Fischer considered the ability relevant to omission only as the ability of bodily movement, the other is that he took in consideration only “the causal control as proximate cause” relevant to omission, with being neglectful of “the causal control as remote cause” which is also relevant to omission.