Traditional village built heritage conservation requires attention to both the preservation of heritage cores and their relationships with peripheral environments. Existing research has extensively examined heritage preservation, spatial change, and external development conditions, but these aspects are often studied separately, leaving core–periphery relationships insufficiently explored. This study adopts a core–periphery perspective to develop a diagnostic framework comprising core preservation (U), peripheral pressures and constraints (P), and peripheral support (S). The framework identifies U–P relational configurations (G) and diagnoses relational conditions using the Core–Periphery Relative Risk Index (RRI), with S assessed separately as complementary information. An empirical analysis combines multi-source spatial data and GIS-based multi-criteria decision analysis for all 22 nationally recognised traditional villages in Jiexiu, Shanxi Province, China, forming a complete county-level case set. The results reveal four U–P configurations. Villages with better-preserved cores may face higher peripheral pressure, while those under lower pressure may have poorly preserved cores. Relational conditions and peripheral support also vary among villages within the same configuration. The study operationalises a core–periphery perspective through a relational diagnostic approach to traditional village built heritage, revealing differences that preservation assessments alone may overlook. It provides an analytical basis for understanding conservation issues and development conditions in traditional villages.