Abstract: Moral bio-enhancement, which uses non-traditional biomedical means to intervene in a subject's moral emotions, is essentially a philosophical approach to moral naturalism. However, some scholars are keen to attribute this approach to a strong reductionist viewpoint and to critique the reductionist limits of moral naturalism scientifically and philosophically, thereby denying the legitimacy of moral bio-enhancement. This argument ignores the fact that reductionism has different shapes in the ontological and methodological sense when discussed in the context of moral bio-enhancement. Moral bio-enhancement asserts the necessity and importance of reductionism for the study of human moral phenomena at the methodological level, while attempting to construct a non-reductionist image at the ontological level in which science and the humanities are integrated and developed. In this way, moral bio-enhancement is fundamentally a weak reductionist version of naturalistic morality. As a weak reductionist version of moral naturalism, moral bio-enhancement gives its own answer by distinguishing between different forms of reductionism. On the one hand, it acknowledges the validity of the naturalistic reductionist approach and provides a naturalistic reduction and explanation of moral properties, which offers a factual basis and objective foundation for bridging the explanatory gap between natural and moral phenomena; on the other hand, the irreducibility of morality exposes the limits of reductionist beliefs and thus defends the specificity and independence of moral phenomena as uniquely human phenomena. Moral bioaugmentation not only brings morality into the laboratory of scientists, but also reveals the significance of the independent existence of moral properties beyond natural properties. On this basis, moral bioaugmentation, limited to a weak reductionist position, establishes its existential space and theoretical legitimacy by confronting the realities of human ethical life.