Abstract: By the third decade of the 21st century, China's population development has reached a historic turning point, with the total fertility rate having remained persistently below 1. 3, marking a new phase of fertility transition. Confronted with the fragmentation, Western-centrism, and other limitations of existing theories in explaining this transition, an explanatory framework is constructed, drawing on the indigenous functionalist resources of Fei Xiaotong's The Reproductive Institution, that centers on the transformation of the principle of social division-of-labor succession. This framework reveals how traditional fertility institutions formed stable structures grounded in status succession, gender-based collaborative division of labor, and family-oriented values. In modern society, the shift from family-based status to individual competition-based selection has triggered the destabilization of gender collaboration systems and the erosion of family-oriented values; compounded by the accelerating effects of the digital-intelligent society, this has ultimately led to a substantial decline in the compatibility between individual survival logics and family- based reproduction patterns, constituting the underlying structural root of the current fertility transition. Based on this framework, the study analyzes the limitations of existing fertility support policies, explores deeper intervention pathways such as socialized childcare and the reconstruction of reproductive value, and looks ahead to the potential reshaping of reproductive institutions by a human-machine society, striving to build an original theory of fertility transition rooted in the Chinese context.