Abstract： Building all-age-friendly cities is a crucial strategy for achieving the national goal of supporting Chinese modernization through high-quality population development. The concept connects life stages, age groups and intergenerational succession with the high-quality development of cities, and aims to provide appropriate environments and resources for the development of all members of society. Based on a systematic reflection on related research and practice in China and abroad, this paper argues that all-age-friendly city building should move beyond an approach focused mainly on vulnerable groups and become a universal agenda for shared development across all age groups. It proposes a goal system that enhances health and well-being across the whole life course, promotes equitable development for all groups and advances intergenerational continuity. Focusing on the intersection of physical space and social space, the paper develops theoretical and methodological support from the combined perspectives of the capacity approach and the opportunity approach. It then proposes planning pathways for all-age-friendly cities, including environmental adaptation, resource coordination and intergenerational practice.