The construction of ecological-cultural composite cross-layer networks represents a crucial pathway for realizing the synergistic expression of the multi-dimensional values embedded in linear cultural heritage. This study takes the administrative areas traversed by the Tianjin section of the Grand Canal as a representative case, notable for its pronounced nesting of ecological and cultural values. Grounded within the theoretical framework of social-ecological system, the research adopts an interdisciplinary methodology that combines morphology spatial pattern analysis, circuit theory model, and social network analysis. Through the integration of these diverse analytical tools, the research proposes a four-step cross-layer network construction pathway termed "identification-connection-coupling-optimization". This innovative approach fundamentally transcends the limitations of conventional modeling paradigms that primarily focus on physical or structural connectivity, and instead pivots toward a value-centric model that integrates ecological function and cultural significance within a unified analytical framework. The results showed that: (1) the ecological source areas in the Tianjin section of the Grand Canal basin have obvious scale heterogeneity and an uneven layout on the spatial scale, while the cultural source areas are primarily distributed along the coast of the Tianjin section of the Grand Canal with the characteristics of large-scale dispersion and small-scale concentration. (2) The ecological corridors in the Tianjin section of the Grand Canal show a general pattern of "dense in the northeast, while sparse in the southwest and northwest", and this imbalance highlights a tangible risk of spatial fragmentation and ecological isolation of small ecological sources in some peripheral or marginal areas; meanwhile, the network of cultural corridors is expanding radially to the periphery with the Tianjin section of the Grand Canal as the core axis, forming a spatial distribution characteristic of "wide in the southern reaches and narrow in the northern sections". (3) The functional subgroups of ecological-cultural composite values show an obvious distribution pattern across administrative boundaries, highlighting the importance of multi-jurisdictional coordination. Based on the synergistic expression and spatial interaction of these values, 6 cross-layer network groups are identified and categorized into 3 distinct types: potential type, unbalanced type, and demonstration type. Corresponding optimization strategies are proposed for both single-layer and integrated network patterns. These strategies aim to enhance spatial coherence, reinforce ecological and cultural synergies, and inform the integrated conservation, spatial governance, and adaptive planning of linear cultural heritage systems. This study thus offers a robust scientific foundation and practical toolkit for promoting value-oriented, cross-scalar management of natural and cultural resources in complex heritage landscapes.